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How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

  • Search for relevant literature
  • Evaluate sources
  • Identify themes, debates, and gaps
  • Outline the structure
  • Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

  • Quick Run-through
  • Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

  • Demonstrate your familiarity with the topic and its scholarly context
  • Develop a theoretical framework and methodology for your research
  • Position your work in relation to other researchers and theorists
  • Show how your research addresses a gap or contributes to a debate
  • Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

Literature review guide

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literature review on previous studies

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

  • Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
  • Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
  • Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
  • Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

  • Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
  • Body image, self-perception, self-esteem, mental health
  • Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

  • Your university’s library catalogue
  • Google Scholar
  • Project Muse (humanities and social sciences)
  • Medline (life sciences and biomedicine)
  • EconLit (economics)
  • Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

  • What question or problem is the author addressing?
  • What are the key concepts and how are they defined?
  • What are the key theories, models, and methods?
  • Does the research use established frameworks or take an innovative approach?
  • What are the results and conclusions of the study?
  • How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
  • What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

  • Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
  • Themes: what questions or concepts recur across the literature?
  • Debates, conflicts and contradictions: where do sources disagree?
  • Pivotal publications: are there any influential theories or studies that changed the direction of the field?
  • Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

  • Most research has focused on young women.
  • There is an increasing interest in the visual aspects of social media.
  • But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

  • Look at what results have emerged in qualitative versus quantitative research
  • Discuss how the topic has been approached by empirical versus theoretical scholarship
  • Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

  • Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
  • Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
  • Critically evaluate: mention the strengths and weaknesses of your sources
  • Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

  • Sampling methods
  • Simple random sampling
  • Stratified sampling
  • Cluster sampling
  • Likert scales
  • Reproducibility

 Statistics

  • Null hypothesis
  • Statistical power
  • Probability distribution
  • Effect size
  • Poisson distribution

Research bias

  • Optimism bias
  • Cognitive bias
  • Implicit bias
  • Hawthorne effect
  • Anchoring bias
  • Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

  • To familiarize yourself with the current state of knowledge on your topic
  • To ensure that you’re not just repeating what others have already done
  • To identify gaps in knowledge and unresolved problems that your research can address
  • To develop your theoretical framework and methodology
  • To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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literature review on previous studies

What is a Literature Review? How to Write It (with Examples)

literature review

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

  • What is the purpose of literature review? 
  • a. Habitat Loss and Species Extinction: 
  • b. Range Shifts and Phenological Changes: 
  • c. Ocean Acidification and Coral Reefs: 
  • d. Adaptive Strategies and Conservation Efforts: 

How to write a good literature review 

  • Choose a Topic and Define the Research Question: 
  • Decide on the Scope of Your Review: 
  • Select Databases for Searches: 
  • Conduct Searches and Keep Track: 
  • Review the Literature: 
  • Organize and Write Your Literature Review: 
  • How to write a literature review faster with Paperpal? 
  • Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

literature review on previous studies

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

1. Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 

2. Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 

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3. Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 

4. Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 

5. Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 

6. Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

literature review on previous studies

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Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

  • Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
  • Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
  • Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
  • Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
  • Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

  • Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
  • Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
  • Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
  • Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
  • Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

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Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

  • Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
  • Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
  • Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
  • Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
  • Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

what is a literature review

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

  • Select a topic that is relevant to your field of study. 
  • Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

  • Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
  • Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
  • Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

  • Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
  • Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

  • Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
  • Record and document your search strategy for transparency and replicability. 
  • Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

  • Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
  • Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
  • Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
  • Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
  • Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

  • Literature review outline should be based on themes, chronological order, or methodological approaches. 
  • Write a clear and coherent narrative that synthesizes the information gathered. 
  • Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
  • Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

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How to write a literature review faster with Paperpal?

Paperpal, an AI writing assistant, integrates powerful academic search capabilities within its writing platform. With the Research feature, you get 100% factual insights, with citations backed by 250M+ verified research articles, directly within your writing interface with the option to save relevant references in your Citation Library. By eliminating the need to switch tabs to find answers to all your research questions, Paperpal saves time and helps you stay focused on your writing.   

Here’s how to use the Research feature:  

  • Ask a question: Get started with a new document on paperpal.com. Click on the “Research” feature and type your question in plain English. Paperpal will scour over 250 million research articles, including conference papers and preprints, to provide you with accurate insights and citations. 
  • Review and Save: Paperpal summarizes the information, while citing sources and listing relevant reads. You can quickly scan the results to identify relevant references and save these directly to your built-in citations library for later access. 
  • Cite with Confidence: Paperpal makes it easy to incorporate relevant citations and references into your writing, ensuring your arguments are well-supported by credible sources. This translates to a polished, well-researched literature review. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a good literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. By combining effortless research with an easy citation process, Paperpal Research streamlines the literature review process and empowers you to write faster and with more confidence. Try Paperpal Research now and see for yourself.  

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

 Annotated Bibliography Literature Review 
Purpose List of citations of books, articles, and other sources with a brief description (annotation) of each source. Comprehensive and critical analysis of existing literature on a specific topic. 
Focus Summary and evaluation of each source, including its relevance, methodology, and key findings. Provides an overview of the current state of knowledge on a particular subject and identifies gaps, trends, and patterns in existing literature. 
Structure Each citation is followed by a concise paragraph (annotation) that describes the source’s content, methodology, and its contribution to the topic. The literature review is organized thematically or chronologically and involves a synthesis of the findings from different sources to build a narrative or argument. 
Length Typically 100-200 words Length of literature review ranges from a few pages to several chapters 
Independence Each source is treated separately, with less emphasis on synthesizing the information across sources. The writer synthesizes information from multiple sources to present a cohesive overview of the topic. 

References 

  • Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
  • Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
  • Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

  • Explains the background of research on a topic.
  • Demonstrates why a topic is significant to a subject area.
  • Discovers relationships between research studies/ideas.
  • Identifies major themes, concepts, and researchers on a topic.
  • Identifies critical gaps and points of disagreement.
  • Discusses further research questions that logically come out of the previous studies.

APA7 Style resources

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APA Style Blog - for those harder to find answers

1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

  • Make sure your research question is not too broad or too narrow.  Is it manageable?
  • Begin writing down terms that are related to your question. These will be useful for searches later.
  • If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

  • This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

  • use the tabs on this guide
  • Find other databases in the Nursing Information Resources web page
  • More on the Medical Library web page
  • ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

  • Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
  • Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
  • Review the abstracts of research studies carefully. This will save you time.
  • Use the bibliographies and references of research studies you find to locate others.
  • Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
  • Ask your librarian for help at any time.
  • Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

  • What was the research question of the study you are reviewing? What were the authors trying to discover?
  • Was the research funded by a source that could influence the findings?
  • What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
  • Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
  • If there are conflicting studies, why do you think that is?
  • How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

  • Review the abstracts carefully.  
  • Keep careful notes so that you may track your thought processes during the research process.
  • Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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Building On The Past: How To Write Previous Studies In Research

Crafting an effective previous study is a foundation for your research. Learn how to write previous studies in research through this guide.

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Have you ever wondered how research builds upon itself, creating a foundation for discoveries and insights? Is it wrong if you indulge in working on previous studies in research and get a new idea out of it?

The significance of previous studies in research cannot be underestimated. Every piece of scholarly work, from groundbreaking research to humble literature reviews , contributes to the ever-expanding area of knowledge. 

In this article, we explore the importance of delving into the archives of research, identifying opportunities for further investigation, and ultimately advancing our understanding of the world around us. Let’s get started and understand how to write previous studies in research . 

Purpose And Scope Of Previous Study In Research

The purpose of previous studies in research is to provide a foundation for new investigations. It helps researchers understand what has already been studied, what knowledge gaps exist, and what questions need further exploration. By looking at what others have done, researchers can build on existing knowledge, avoid repeating the same work, and ensure their study contributes something valuable to the field. It also helps validate their research design and methods, making their findings more credible.

The scope of previous studies in research refers to the range of literature and sources that researchers consider relevant to their own study. It involves selecting and reviewing studies that directly relate to their research topic and objectives. Researchers should focus on recent and up-to-date works, including both influential studies and the latest advancements in the field. By being selective and inclusive, they can gain a well-rounded understanding of what has been done before, guiding them to ask meaningful research questions and making their study more impactful.

How To Write Previous Studies In Research

To write the previous studies, you first need to understand the steps in crafting a literature review and the limitations involved. So firstly, let’s understand what is a literature review:

What Is Literature Review?

A literature review is a critical and comprehensive evaluation of existing published research, scholarly articles, books, and other sources relevant to a particular topic or research question. It serves as a crucial component of academic research and helps to establish the context, identify gaps in knowledge, and provide the theoretical framework for the new study. A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature and provides the basis for formulating research objectives and hypotheses.

Also read: What Is A Literature Review? Get The Concept And Start Using It

Literature Review Process

The literature review process typically involves the following steps:

Defining The Research Question

The process starts by clearly defining the research question or topic that the literature review aims to address. A well-defined question helps in narrowing down the search for relevant literature.

Conducting A Comprehensive Search

Researchers then conduct a systematic search for existing literature using academic databases, libraries, online journals, and other reputable sources. Keywords and search terms related to the research question are used to identify relevant studies.

Evaluating The Quality Of Sources

The selected sources are critically evaluated for their quality, credibility, and relevance to the research topic. Researchers consider factors such as the reputation of the authors, the rigor of the research methodology, and the publication venue.

Summarizing And Synthesizing

Researchers summarize the key findings and main points from each selected source. They also identify common themes, trends, and conflicting viewpoints across the literature.

Organizing The Literature

The information gathered from the literature review is organized in a structured manner. Researchers may use themes, categories, or chronological order to present the findings effectively.

Writing The Literature Review

The literature review is then written, incorporating the synthesized information into a coherent narrative. The review should highlight the significance of previous studies, their limitations, and their implications for the new research.

Citing And Referencing

Proper citations and references are provided for all the sources included in the literature review. This ensures academic integrity and acknowledges the work of other researchers.

Also read: Literature Mapping in Scientific Research: A Comprehensive Review

How To Organize And Evaluate Your Literature Review?

Organizing and evaluating sources for your literature review is a crucial process that involves systematically gathering relevant academic materials and assessing their credibility and relevance to your research topic. 

Begin by clearly defining your research question or focus, which will guide your search for appropriate sources. Utilize academic databases, journals, books, and reputable online platforms to gather a diverse range of scholarly materials. 

As you collect sources, categorize them based on their themes, methodologies, or key arguments to facilitate a coherent and logical structure for your literature review. Additionally, critically evaluate each source’s authority, currency, objectivity, and reliability to ensure you include high-quality and trustworthy information in your review. 

By employing a rigorous approach to organizing and evaluating your sources, you will enhance the academic rigor and impact of your literature review.

Limitations Of Previous Studies In Research

The limitations of previous studies are common aspects that researchers should consider while conducting a literature review or developing their own research. These limitations may include:

Sample Size And Representativeness

Some studies may have small sample sizes, which can limit the generalizability of their findings to larger populations or diverse groups. Non-representative samples may also introduce bias into the results .

Research Design And Methodology

Previous studies may have used different research designs or methodologies that could impact the reliability and validity of their results. Flaws in the study design or data collection methods may affect the accuracy of the findings.

Data Quality And Availability

Studies may rely on secondary data sources or data with inherent limitations, potentially affecting the accuracy and completeness of the information used for analysis.

Scope And Generalizability

The scope of a study might be narrow, focusing on a specific population, region, or time period, making it challenging to apply the findings to broader contexts.

Publication Bias

Studies that show statistically significant or positive results may be more likely to get published, while studies with null or non-significant results might go unpublished, leading to a biased representation of the literature.

Ethical Considerations

Ethical issues in data collection or research conduct, such as inadequate informed consent or potential harm to participants, could limit the usefulness or ethical soundness of previous studies.

Related article: What Are The Limitations In Research And How To Write Them?

Identifying Opportunities For Future Research Based On Previous Studies

Identifying opportunities for future research based on previous studies is an essential aspect of conducting a literature review and advancing knowledge in a particular field. Here are some strategies to identify such opportunities:

Unanswered Questions

Look for gaps in the existing literature where important questions remain unanswered or areas where conflicting or inconclusive results have been reported. These gaps represent opportunities for future research to delve deeper into the topic and provide more comprehensive insights.

Emerging Trends

Identify emerging trends or new developments within the field. These can indicate areas that are gaining significance but may not yet have been extensively studied. Exploring these emerging trends can contribute to the cutting edge of research.

Limitations Of Previous Studies

As mentioned earlier, assess the limitations of previous studies. These limitations can point to areas that need further investigation, using improved methodologies or data sources to overcome the shortcomings of earlier research.

Replication Studies

Consider replicating studies that have produced significant findings but have not been replicated by other researchers. Replication studies help validate and strengthen the robustness of existing findings.

Cross-Disciplinary Research

Look for opportunities to integrate knowledge and methodologies from different disciplines. Combining insights from diverse fields can lead to innovative research and fresh perspectives on existing problems.

The Bottom Line

The role of previous studies in research and literature review is crucial in shaping knowledge within any field. Through a comprehensive and critical examination of existing literature, researchers can identify gaps, trends, limitations, and unanswered questions that provide valuable opportunities for future investigation. 

Previous studies serve as a foundation upon which new research can build, validate, and extend existing findings, or challenge established paradigms. By acknowledging and understanding the contributions and limitations of past research, scholars can design more robust studies, explore emerging trends, and engage in cross-disciplinary collaborations to further enrich our understanding of complex phenomena.

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About Sowjanya Pedada

Sowjanya is a passionate writer and an avid reader. She holds MBA in Agribusiness Management and now is working as a content writer. She loves to play with words and hopes to make a difference in the world through her writings. Apart from writing, she is interested in reading fiction novels and doing craftwork. She also loves to travel and explore different cuisines and spend time with her family and friends.

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How to Make a Literature Review in Research (RRL Example)

literature review on previous studies

What is an RRL in a research paper?

A relevant review of the literature (RRL) is an objective, concise, critical summary of published research literature relevant to a topic being researched in an article. In an RRL, you discuss knowledge and findings from existing literature relevant to your study topic. If there are conflicts or gaps in existing literature, you can also discuss these in your review, as well as how you will confront these missing elements or resolve these issues in your study.

To complete an RRL, you first need to collect relevant literature; this can include online and offline sources. Save all of your applicable resources as you will need to include them in your paper. When looking through these sources, take notes and identify concepts of each source to describe in the review of the literature.

A good RRL does NOT:

A literature review does not simply reference and list all of the material you have cited in your paper.

  • Presenting material that is not directly relevant to your study will distract and frustrate the reader and make them lose sight of the purpose of your study.
  • Starting a literature review with “A number of scholars have studied the relationship between X and Y” and simply listing who has studied the topic and what each scholar concluded is not going to strengthen your paper.

A good RRL DOES:

  • Present a brief typology that orders articles and books into groups to help readers focus on unresolved debates, inconsistencies, tensions, and new questions about a research topic.
  • Summarize the most relevant and important aspects of the scientific literature related to your area of research
  • Synthesize what has been done in this area of research and by whom, highlight what previous research indicates about a topic, and identify potential gaps and areas of disagreement in the field
  • Give the reader an understanding of the background of the field and show which studies are important—and highlight errors in previous studies

How long is a review of the literature for a research paper?

The length of a review of the literature depends on its purpose and target readership and can vary significantly in scope and depth. In a dissertation, thesis, or standalone review of literature, it is usually a full chapter of the text (at least 20 pages). Whereas, a standard research article or school assignment literature review section could only be a few paragraphs in the Introduction section .

Building Your Literature Review Bookshelf

One way to conceive of a literature review is to think about writing it as you would build a bookshelf. You don’t need to cut each piece by yourself from scratch. Rather, you can take the pieces that other researchers have cut out and put them together to build a framework on which to hang your own “books”—that is, your own study methods, results, and conclusions.

literature review bookshelf

What Makes a Good Literature Review?

The contents of a literature review (RRL) are determined by many factors, including its precise purpose in the article, the degree of consensus with a given theory or tension between competing theories, the length of the article, the number of previous studies existing in the given field, etc. The following are some of the most important elements that a literature review provides.

Historical background for your research

Analyze what has been written about your field of research to highlight what is new and significant in your study—or how the analysis itself contributes to the understanding of this field, even in a small way. Providing a historical background also demonstrates to other researchers and journal editors your competency in discussing theoretical concepts. You should also make sure to understand how to paraphrase scientific literature to avoid plagiarism in your work.

The current context of your research

Discuss central (or peripheral) questions, issues, and debates in the field. Because a field is constantly being updated by new work, you can show where your research fits into this context and explain developments and trends in research.

A discussion of relevant theories and concepts

Theories and concepts should provide the foundation for your research. For example, if you are researching the relationship between ecological environments and human populations, provide models and theories that focus on specific aspects of this connection to contextualize your study. If your study asks a question concerning sustainability, mention a theory or model that underpins this concept. If it concerns invasive species, choose material that is focused in this direction.

Definitions of relevant terminology

In the natural sciences, the meaning of terms is relatively straightforward and consistent. But if you present a term that is obscure or context-specific, you should define the meaning of the term in the Introduction section (if you are introducing a study) or in the summary of the literature being reviewed.

Description of related relevant research

Include a description of related research that shows how your work expands or challenges earlier studies or fills in gaps in previous work. You can use your literature review as evidence of what works, what doesn’t, and what is missing in the field.

Supporting evidence for a practical problem or issue your research is addressing that demonstrates its importance: Referencing related research establishes your area of research as reputable and shows you are building upon previous work that other researchers have deemed significant.

Types of Literature Reviews

Literature reviews can differ in structure, length, amount, and breadth of content included. They can range from selective (a very narrow area of research or only a single work) to comprehensive (a larger amount or range of works). They can also be part of a larger work or stand on their own.

types of literature reviews

  • A course assignment is an example of a selective, stand-alone work. It focuses on a small segment of the literature on a topic and makes up an entire work on its own.
  • The literature review in a dissertation or thesis is both comprehensive and helps make up a larger work.
  • A majority of journal articles start with a selective literature review to provide context for the research reported in the study; such a literature review is usually included in the Introduction section (but it can also follow the presentation of the results in the Discussion section ).
  • Some literature reviews are both comprehensive and stand as a separate work—in this case, the entire article analyzes the literature on a given topic.

Literature Reviews Found in Academic Journals

The two types of literature reviews commonly found in journals are those introducing research articles (studies and surveys) and stand-alone literature analyses. They can differ in their scope, length, and specific purpose.

Literature reviews introducing research articles

The literature review found at the beginning of a journal article is used to introduce research related to the specific study and is found in the Introduction section, usually near the end. It is shorter than a stand-alone review because it must be limited to very specific studies and theories that are directly relevant to the current study. Its purpose is to set research precedence and provide support for the study’s theory, methods, results, and/or conclusions. Not all research articles contain an explicit review of the literature, but most do, whether it is a discrete section or indistinguishable from the rest of the Introduction.

How to structure a literature review for an article

When writing a literature review as part of an introduction to a study, simply follow the structure of the Introduction and move from the general to the specific—presenting the broadest background information about a topic first and then moving to specific studies that support your rationale , finally leading to your hypothesis statement. Such a literature review is often indistinguishable from the Introduction itself—the literature is INTRODUCING the background and defining the gaps your study aims to fill.

The stand-alone literature review

The literature review published as a stand-alone article presents and analyzes as many of the important publications in an area of study as possible to provide background information and context for a current area of research or a study. Stand-alone reviews are an excellent resource for researchers when they are first searching for the most relevant information on an area of study.

Such literature reviews are generally a bit broader in scope and can extend further back in time. This means that sometimes a scientific literature review can be highly theoretical, in addition to focusing on specific methods and outcomes of previous studies. In addition, all sections of such a “review article” refer to existing literature rather than describing the results of the authors’ own study.

In addition, this type of literature review is usually much longer than the literature review introducing a study. At the end of the review follows a conclusion that once again explicitly ties all of the cited works together to show how this analysis is itself a contribution to the literature. While not absolutely necessary, such articles often include the terms “Literature Review” or “Review of the Literature” in the title. Whether or not that is necessary or appropriate can also depend on the specific author instructions of the target journal. Have a look at this article for more input on how to compile a stand-alone review article that is insightful and helpful for other researchers in your field.

literature review examples

How to Write a Literature Review in 6 Steps

So how do authors turn a network of articles into a coherent review of relevant literature?

Writing a literature review is not usually a linear process—authors often go back and check the literature while reformulating their ideas or making adjustments to their study. Sometimes new findings are published before a study is completed and need to be incorporated into the current work. This also means you will not be writing the literature review at any one time, but constantly working on it before, during, and after your study is complete.

Here are some steps that will help you begin and follow through on your literature review.

Step 1: Choose a topic to write about—focus on and explore this topic.

Choose a topic that you are familiar with and highly interested in analyzing; a topic your intended readers and researchers will find interesting and useful; and a topic that is current, well-established in the field, and about which there has been sufficient research conducted for a review. This will help you find the “sweet spot” for what to focus on.

Step 2: Research and collect all the scholarly information on the topic that might be pertinent to your study.

This includes scholarly articles, books, conventions, conferences, dissertations, and theses—these and any other academic work related to your area of study is called “the literature.”

Step 3: Analyze the network of information that extends or responds to the major works in your area; select the material that is most useful.

Use thought maps and charts to identify intersections in the research and to outline important categories; select the material that will be most useful to your review.

Step 4: Describe and summarize each article—provide the essential information of the article that pertains to your study.

Determine 2-3 important concepts (depending on the length of your article) that are discussed in the literature; take notes about all of the important aspects of this study relevant to the topic being reviewed.

For example, in a given study, perhaps some of the main concepts are X, Y, and Z. Note these concepts and then write a brief summary about how the article incorporates them. In reviews that introduce a study, these can be relatively short. In stand-alone reviews, there may be significantly more texts and more concepts.

Step 5: Demonstrate how these concepts in the literature relate to what you discovered in your study or how the literature connects the concepts or topics being discussed.

In a literature review intro for an article, this information might include a summary of the results or methods of previous studies that correspond to and/or confirm those sections in your own study. For a stand-alone literature review, this may mean highlighting the concepts in each article and showing how they strengthen a hypothesis or show a pattern.

Discuss unaddressed issues in previous studies. These studies that are missing something you address are important to include in your literature review. In addition, those works whose theories and conclusions directly support your findings will be valuable to review here.

Step 6: Identify relationships in the literature and develop and connect your own ideas to them.

This is essentially the same as step 5 but focused on the connections between the literature and the current study or guiding concepts or arguments of the paper, not only on the connections between the works themselves.

Your hypothesis, argument, or guiding concept is the “golden thread” that will ultimately tie the works together and provide readers with specific insights they didn’t have before reading your literature review. Make sure you know where to put the research question , hypothesis, or statement of the problem in your research paper so that you guide your readers logically and naturally from your introduction of earlier work and evidence to the conclusions you want them to draw from the bigger picture.

Your literature review will not only cover publications on your topics but will include your own ideas and contributions. By following these steps you will be telling the specific story that sets the background and shows the significance of your research and you can turn a network of related works into a focused review of the literature.

Literature Review (RRL) Examples

Because creating sample literature reviews would take too long and not properly capture the nuances and detailed information needed for a good review, we have included some links to different types of literature reviews below. You can find links to more literature reviews in these categories by visiting the TUS Library’s website . Sample literature reviews as part of an article, dissertation, or thesis:

  • Critical Thinking and Transferability: A Review of the Literature (Gwendolyn Reece)
  • Building Customer Loyalty: A Customer Experience Based Approach in a Tourism Context (Martina Donnelly)

Sample stand-alone literature reviews

  • Literature Review on Attitudes towards Disability (National Disability Authority)
  • The Effects of Communication Styles on Marital Satisfaction (Hannah Yager)

Additional Literature Review Format Guidelines

In addition to the content guidelines above, authors also need to check which style guidelines to use ( APA , Chicago, MLA, etc.) and what specific rules the target journal might have for how to structure such articles or how many studies to include—such information can usually be found on the journals’ “Guide for Authors” pages. Additionally, use one of the four Wordvice citation generators below, choosing the citation style needed for your paper:

Wordvice Writing and Academic Editing Resources

Finally, after you have finished drafting your literature review, be sure to receive professional proofreading services , including paper editing for your academic work. A competent proofreader who understands academic writing conventions and the specific style guides used by academic journals will ensure that your paper is ready for publication in your target journal.

See our academic resources for further advice on references in your paper , how to write an abstract , how to write a research paper title, how to impress the editor of your target journal with a perfect cover letter , and dozens of other research writing and publication topics.

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Approaching literature review for academic purposes: The Literature Review Checklist

Debora f.b. leite.

I Departamento de Ginecologia e Obstetricia, Faculdade de Ciencias Medicas, Universidade Estadual de Campinas, Campinas, SP, BR

II Universidade Federal de Pernambuco, Pernambuco, PE, BR

III Hospital das Clinicas, Universidade Federal de Pernambuco, Pernambuco, PE, BR

Maria Auxiliadora Soares Padilha

Jose g. cecatti.

A sophisticated literature review (LR) can result in a robust dissertation/thesis by scrutinizing the main problem examined by the academic study; anticipating research hypotheses, methods and results; and maintaining the interest of the audience in how the dissertation/thesis will provide solutions for the current gaps in a particular field. Unfortunately, little guidance is available on elaborating LRs, and writing an LR chapter is not a linear process. An LR translates students’ abilities in information literacy, the language domain, and critical writing. Students in postgraduate programs should be systematically trained in these skills. Therefore, this paper discusses the purposes of LRs in dissertations and theses. Second, the paper considers five steps for developing a review: defining the main topic, searching the literature, analyzing the results, writing the review and reflecting on the writing. Ultimately, this study proposes a twelve-item LR checklist. By clearly stating the desired achievements, this checklist allows Masters and Ph.D. students to continuously assess their own progress in elaborating an LR. Institutions aiming to strengthen students’ necessary skills in critical academic writing should also use this tool.

INTRODUCTION

Writing the literature review (LR) is often viewed as a difficult task that can be a point of writer’s block and procrastination ( 1 ) in postgraduate life. Disagreements on the definitions or classifications of LRs ( 2 ) may confuse students about their purpose and scope, as well as how to perform an LR. Interestingly, at many universities, the LR is still an important element in any academic work, despite the more recent trend of producing scientific articles rather than classical theses.

The LR is not an isolated section of the thesis/dissertation or a copy of the background section of a research proposal. It identifies the state-of-the-art knowledge in a particular field, clarifies information that is already known, elucidates implications of the problem being analyzed, links theory and practice ( 3 - 5 ), highlights gaps in the current literature, and places the dissertation/thesis within the research agenda of that field. Additionally, by writing the LR, postgraduate students will comprehend the structure of the subject and elaborate on their cognitive connections ( 3 ) while analyzing and synthesizing data with increasing maturity.

At the same time, the LR transforms the student and hints at the contents of other chapters for the reader. First, the LR explains the research question; second, it supports the hypothesis, objectives, and methods of the research project; and finally, it facilitates a description of the student’s interpretation of the results and his/her conclusions. For scholars, the LR is an introductory chapter ( 6 ). If it is well written, it demonstrates the student’s understanding of and maturity in a particular topic. A sound and sophisticated LR can indicate a robust dissertation/thesis.

A consensus on the best method to elaborate a dissertation/thesis has not been achieved. The LR can be a distinct chapter or included in different sections; it can be part of the introduction chapter, part of each research topic, or part of each published paper ( 7 ). However, scholars view the LR as an integral part of the main body of an academic work because it is intrinsically connected to other sections ( Figure 1 ) and is frequently present. The structure of the LR depends on the conventions of a particular discipline, the rules of the department, and the student’s and supervisor’s areas of expertise, needs and interests.

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Object name is cln-74-e1403-g001.jpg

Interestingly, many postgraduate students choose to submit their LR to peer-reviewed journals. As LRs are critical evaluations of current knowledge, they are indeed publishable material, even in the form of narrative or systematic reviews. However, systematic reviews have specific patterns 1 ( 8 ) that may not entirely fit with the questions posed in the dissertation/thesis. Additionally, the scope of a systematic review may be too narrow, and the strict criteria for study inclusion may omit important information from the dissertation/thesis. Therefore, this essay discusses the definition of an LR is and methods to develop an LR in the context of an academic dissertation/thesis. Finally, we suggest a checklist to evaluate an LR.

WHAT IS A LITERATURE REVIEW IN A THESIS?

Conducting research and writing a dissertation/thesis translates rational thinking and enthusiasm ( 9 ). While a strong body of literature that instructs students on research methodology, data analysis and writing scientific papers exists, little guidance on performing LRs is available. The LR is a unique opportunity to assess and contrast various arguments and theories, not just summarize them. The research results should not be discussed within the LR, but the postgraduate student tends to write a comprehensive LR while reflecting on his or her own findings ( 10 ).

Many people believe that writing an LR is a lonely and linear process. Supervisors or the institutions assume that the Ph.D. student has mastered the relevant techniques and vocabulary associated with his/her subject and conducts a self-reflection about previously published findings. Indeed, while elaborating the LR, the student should aggregate diverse skills, which mainly rely on his/her own commitment to mastering them. Thus, less supervision should be required ( 11 ). However, the parameters described above might not currently be the case for many students ( 11 , 12 ), and the lack of formal and systematic training on writing LRs is an important concern ( 11 ).

An institutional environment devoted to active learning will provide students the opportunity to continuously reflect on LRs, which will form a dialogue between the postgraduate student and the current literature in a particular field ( 13 ). Postgraduate students will be interpreting studies by other researchers, and, according to Hart (1998) ( 3 ), the outcomes of the LR in a dissertation/thesis include the following:

  • To identify what research has been performed and what topics require further investigation in a particular field of knowledge;
  • To determine the context of the problem;
  • To recognize the main methodologies and techniques that have been used in the past;
  • To place the current research project within the historical, methodological and theoretical context of a particular field;
  • To identify significant aspects of the topic;
  • To elucidate the implications of the topic;
  • To offer an alternative perspective;
  • To discern how the studied subject is structured;
  • To improve the student’s subject vocabulary in a particular field; and
  • To characterize the links between theory and practice.

A sound LR translates the postgraduate student’s expertise in academic and scientific writing: it expresses his/her level of comfort with synthesizing ideas ( 11 ). The LR reveals how well the postgraduate student has proceeded in three domains: an effective literature search, the language domain, and critical writing.

Effective literature search

All students should be trained in gathering appropriate data for specific purposes, and information literacy skills are a cornerstone. These skills are defined as “an individual’s ability to know when they need information, to identify information that can help them address the issue or problem at hand, and to locate, evaluate, and use that information effectively” ( 14 ). Librarian support is of vital importance in coaching the appropriate use of Boolean logic (AND, OR, NOT) and other tools for highly efficient literature searches (e.g., quotation marks and truncation), as is the appropriate management of electronic databases.

Language domain

Academic writing must be concise and precise: unnecessary words distract the reader from the essential content ( 15 ). In this context, reading about issues distant from the research topic ( 16 ) may increase students’ general vocabulary and familiarity with grammar. Ultimately, reading diverse materials facilitates and encourages the writing process itself.

Critical writing

Critical judgment includes critical reading, thinking and writing. It supposes a student’s analytical reflection about what he/she has read. The student should delineate the basic elements of the topic, characterize the most relevant claims, identify relationships, and finally contrast those relationships ( 17 ). Each scientific document highlights the perspective of the author, and students will become more confident in judging the supporting evidence and underlying premises of a study and constructing their own counterargument as they read more articles. A paucity of integration or contradictory perspectives indicates lower levels of cognitive complexity ( 12 ).

Thus, while elaborating an LR, the postgraduate student should achieve the highest category of Bloom’s cognitive skills: evaluation ( 12 ). The writer should not only summarize data and understand each topic but also be able to make judgments based on objective criteria, compare resources and findings, identify discrepancies due to methodology, and construct his/her own argument ( 12 ). As a result, the student will be sufficiently confident to show his/her own voice .

Writing a consistent LR is an intense and complex activity that reveals the training and long-lasting academic skills of a writer. It is not a lonely or linear process. However, students are unlikely to be prepared to write an LR if they have not mastered the aforementioned domains ( 10 ). An institutional environment that supports student learning is crucial.

Different institutions employ distinct methods to promote students’ learning processes. First, many universities propose modules to develop behind the scenes activities that enhance self-reflection about general skills (e.g., the skills we have mastered and the skills we need to develop further), behaviors that should be incorporated (e.g., self-criticism about one’s own thoughts), and each student’s role in the advancement of his/her field. Lectures or workshops about LRs themselves are useful because they describe the purposes of the LR and how it fits into the whole picture of a student’s work. These activities may explain what type of discussion an LR must involve, the importance of defining the correct scope, the reasons to include a particular resource, and the main role of critical reading.

Some pedagogic services that promote a continuous improvement in study and academic skills are equally important. Examples include workshops about time management, the accomplishment of personal objectives, active learning, and foreign languages for nonnative speakers. Additionally, opportunities to converse with other students promotes an awareness of others’ experiences and difficulties. Ultimately, the supervisor’s role in providing feedback and setting deadlines is crucial in developing students’ abilities and in strengthening students’ writing quality ( 12 ).

HOW SHOULD A LITERATURE REVIEW BE DEVELOPED?

A consensus on the appropriate method for elaborating an LR is not available, but four main steps are generally accepted: defining the main topic, searching the literature, analyzing the results, and writing ( 6 ). We suggest a fifth step: reflecting on the information that has been written in previous publications ( Figure 2 ).

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First step: Defining the main topic

Planning an LR is directly linked to the research main question of the thesis and occurs in parallel to students’ training in the three domains discussed above. The planning stage helps organize ideas, delimit the scope of the LR ( 11 ), and avoid the wasting of time in the process. Planning includes the following steps:

  • Reflecting on the scope of the LR: postgraduate students will have assumptions about what material must be addressed and what information is not essential to an LR ( 13 , 18 ). Cooper’s Taxonomy of Literature Reviews 2 systematizes the writing process through six characteristics and nonmutually exclusive categories. The focus refers to the reviewer’s most important points of interest, while the goals concern what students want to achieve with the LR. The perspective assumes answers to the student’s own view of the LR and how he/she presents a particular issue. The coverage defines how comprehensive the student is in presenting the literature, and the organization determines the sequence of arguments. The audience is defined as the group for whom the LR is written.
  • Designating sections and subsections: Headings and subheadings should be specific, explanatory and have a coherent sequence throughout the text ( 4 ). They simulate an inverted pyramid, with an increasing level of reflection and depth of argument.
  • Identifying keywords: The relevant keywords for each LR section should be listed to guide the literature search. This list should mirror what Hart (1998) ( 3 ) advocates as subject vocabulary . The keywords will also be useful when the student is writing the LR since they guide the reader through the text.
  • Delineating the time interval and language of documents to be retrieved in the second step. The most recently published documents should be considered, but relevant texts published before a predefined cutoff year can be included if they are classic documents in that field. Extra care should be employed when translating documents.

Second step: Searching the literature

The ability to gather adequate information from the literature must be addressed in postgraduate programs. Librarian support is important, particularly for accessing difficult texts. This step comprises the following components:

  • Searching the literature itself: This process consists of defining which databases (electronic or dissertation/thesis repositories), official documents, and books will be searched and then actively conducting the search. Information literacy skills have a central role in this stage. While searching electronic databases, controlled vocabulary (e.g., Medical Subject Headings, or MeSH, for the PubMed database) or specific standardized syntax rules may need to be applied.

In addition, two other approaches are suggested. First, a review of the reference list of each document might be useful for identifying relevant publications to be included and important opinions to be assessed. This step is also relevant for referencing the original studies and leading authors in that field. Moreover, students can directly contact the experts on a particular topic to consult with them regarding their experience or use them as a source of additional unpublished documents.

Before submitting a dissertation/thesis, the electronic search strategy should be repeated. This process will ensure that the most recently published papers will be considered in the LR.

  • Selecting documents for inclusion: Generally, the most recent literature will be included in the form of published peer-reviewed papers. Assess books and unpublished material, such as conference abstracts, academic texts and government reports, are also important to assess since the gray literature also offers valuable information. However, since these materials are not peer-reviewed, we recommend that they are carefully added to the LR.

This task is an important exercise in time management. First, students should read the title and abstract to understand whether that document suits their purposes, addresses the research question, and helps develop the topic of interest. Then, they should scan the full text, determine how it is structured, group it with similar documents, and verify whether other arguments might be considered ( 5 ).

Third step: Analyzing the results

Critical reading and thinking skills are important in this step. This step consists of the following components:

  • Reading documents: The student may read various texts in depth according to LR sections and subsections ( defining the main topic ), which is not a passive activity ( 1 ). Some questions should be asked to practice critical analysis skills, as listed below. Is the research question evident and articulated with previous knowledge? What are the authors’ research goals and theoretical orientations, and how do they interact? Are the authors’ claims related to other scholars’ research? Do the authors consider different perspectives? Was the research project designed and conducted properly? Are the results and discussion plausible, and are they consistent with the research objectives and methodology? What are the strengths and limitations of this work? How do the authors support their findings? How does this work contribute to the current research topic? ( 1 , 19 )
  • Taking notes: Students who systematically take notes on each document are more readily able to establish similarities or differences with other documents and to highlight personal observations. This approach reinforces the student’s ideas about the next step and helps develop his/her own academic voice ( 1 , 13 ). Voice recognition software ( 16 ), mind maps ( 5 ), flowcharts, tables, spreadsheets, personal comments on the referenced texts, and note-taking apps are all available tools for managing these observations, and the student him/herself should use the tool that best improves his/her learning. Additionally, when a student is considering submitting an LR to a peer-reviewed journal, notes should be taken on the activities performed in all five steps to ensure that they are able to be replicated.

Fourth step: Writing

The recognition of when a student is able and ready to write after a sufficient period of reading and thinking is likely a difficult task. Some students can produce a review in a single long work session. However, as discussed above, writing is not a linear process, and students do not need to write LRs according to a specific sequence of sections. Writing an LR is a time-consuming task, and some scholars believe that a period of at least six months is sufficient ( 6 ). An LR, and academic writing in general, expresses the writer’s proper thoughts, conclusions about others’ work ( 6 , 10 , 13 , 16 ), and decisions about methods to progress in the chosen field of knowledge. Thus, each student is expected to present a different learning and writing trajectory.

In this step, writing methods should be considered; then, editing, citing and correct referencing should complete this stage, at least temporarily. Freewriting techniques may be a good starting point for brainstorming ideas and improving the understanding of the information that has been read ( 1 ). Students should consider the following parameters when creating an agenda for writing the LR: two-hour writing blocks (at minimum), with prespecified tasks that are possible to complete in one section; short (minutes) and long breaks (days or weeks) to allow sufficient time for mental rest and reflection; and short- and long-term goals to motivate the writing itself ( 20 ). With increasing experience, this scheme can vary widely, and it is not a straightforward rule. Importantly, each discipline has a different way of writing ( 1 ), and each department has its own preferred styles for citations and references.

Fifth step: Reflecting on the writing

In this step, the postgraduate student should ask him/herself the same questions as in the analyzing the results step, which can take more time than anticipated. Ambiguities, repeated ideas, and a lack of coherence may not be noted when the student is immersed in the writing task for long periods. The whole effort will likely be a work in progress, and continuous refinements in the written material will occur once the writing process has begun.

LITERATURE REVIEW CHECKLIST

In contrast to review papers, the LR of a dissertation/thesis should not be a standalone piece or work. Instead, it should present the student as a scholar and should maintain the interest of the audience in how that dissertation/thesis will provide solutions for the current gaps in a particular field.

A checklist for evaluating an LR is convenient for students’ continuous academic development and research transparency: it clearly states the desired achievements for the LR of a dissertation/thesis. Here, we present an LR checklist developed from an LR scoring rubric ( 11 ). For a critical analysis of an LR, we maintain the five categories but offer twelve criteria that are not scaled ( Figure 3 ). The criteria all have the same importance and are not mutually exclusive.

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First category: Coverage

1. justified criteria exist for the inclusion and exclusion of literature in the review.

This criterion builds on the main topic and areas covered by the LR ( 18 ). While experts may be confident in retrieving and selecting literature, postgraduate students must convince their audience about the adequacy of their search strategy and their reasons for intentionally selecting what material to cover ( 11 ). References from different fields of knowledge provide distinct perspective, but narrowing the scope of coverage may be important in areas with a large body of existing knowledge.

Second category: Synthesis

2. a critical examination of the state of the field exists.

A critical examination is an assessment of distinct aspects in the field ( 1 ) along with a constructive argument. It is not a negative critique but an expression of the student’s understanding of how other scholars have added to the topic ( 1 ), and the student should analyze and contextualize contradictory statements. A writer’s personal bias (beliefs or political involvement) have been shown to influence the structure and writing of a document; therefore, the cultural and paradigmatic background guide how the theories are revised and presented ( 13 ). However, an honest judgment is important when considering different perspectives.

3. The topic or problem is clearly placed in the context of the broader scholarly literature

The broader scholarly literature should be related to the chosen main topic for the LR ( how to develop the literature review section). The LR can cover the literature from one or more disciplines, depending on its scope, but it should always offer a new perspective. In addition, students should be careful in citing and referencing previous publications. As a rule, original studies and primary references should generally be included. Systematic and narrative reviews present summarized data, and it may be important to cite them, particularly for issues that should be understood but do not require a detailed description. Similarly, quotations highlight the exact statement from another publication. However, excessive referencing may disclose lower levels of analysis and synthesis by the student.

4. The LR is critically placed in the historical context of the field

Situating the LR in its historical context shows the level of comfort of the student in addressing a particular topic. Instead of only presenting statements and theories in a temporal approach, which occasionally follows a linear timeline, the LR should authentically characterize the student’s academic work in the state-of-art techniques in their particular field of knowledge. Thus, the LR should reinforce why the dissertation/thesis represents original work in the chosen research field.

5. Ambiguities in definitions are considered and resolved

Distinct theories on the same topic may exist in different disciplines, and one discipline may consider multiple concepts to explain one topic. These misunderstandings should be addressed and contemplated. The LR should not synthesize all theories or concepts at the same time. Although this approach might demonstrate in-depth reading on a particular topic, it can reveal a student’s inability to comprehend and synthesize his/her research problem.

6. Important variables and phenomena relevant to the topic are articulated

The LR is a unique opportunity to articulate ideas and arguments and to purpose new relationships between them ( 10 , 11 ). More importantly, a sound LR will outline to the audience how these important variables and phenomena will be addressed in the current academic work. Indeed, the LR should build a bidirectional link with the remaining sections and ground the connections between all of the sections ( Figure 1 ).

7. A synthesized new perspective on the literature has been established

The LR is a ‘creative inquiry’ ( 13 ) in which the student elaborates his/her own discourse, builds on previous knowledge in the field, and describes his/her own perspective while interpreting others’ work ( 13 , 17 ). Thus, students should articulate the current knowledge, not accept the results at face value ( 11 , 13 , 17 ), and improve their own cognitive abilities ( 12 ).

Third category: Methodology

8. the main methodologies and research techniques that have been used in the field are identified and their advantages and disadvantages are discussed.

The LR is expected to distinguish the research that has been completed from investigations that remain to be performed, address the benefits and limitations of the main methods applied to date, and consider the strategies for addressing the expected limitations described above. While placing his/her research within the methodological context of a particular topic, the LR will justify the methodology of the study and substantiate the student’s interpretations.

9. Ideas and theories in the field are related to research methodologies

The audience expects the writer to analyze and synthesize methodological approaches in the field. The findings should be explained according to the strengths and limitations of previous research methods, and students must avoid interpretations that are not supported by the analyzed literature. This criterion translates to the student’s comprehension of the applicability and types of answers provided by different research methodologies, even those using a quantitative or qualitative research approach.

Fourth category: Significance

10. the scholarly significance of the research problem is rationalized.

The LR is an introductory section of a dissertation/thesis and will present the postgraduate student as a scholar in a particular field ( 11 ). Therefore, the LR should discuss how the research problem is currently addressed in the discipline being investigated or in different disciplines, depending on the scope of the LR. The LR explains the academic paradigms in the topic of interest ( 13 ) and methods to advance the field from these starting points. However, an excess number of personal citations—whether referencing the student’s research or studies by his/her research team—may reflect a narrow literature search and a lack of comprehensive synthesis of ideas and arguments.

11. The practical significance of the research problem is rationalized

The practical significance indicates a student’s comprehensive understanding of research terminology (e.g., risk versus associated factor), methodology (e.g., efficacy versus effectiveness) and plausible interpretations in the context of the field. Notably, the academic argument about a topic may not always reflect the debate in real life terms. For example, using a quantitative approach in epidemiology, statistically significant differences between groups do not explain all of the factors involved in a particular problem ( 21 ). Therefore, excessive faith in p -values may reflect lower levels of critical evaluation of the context and implications of a research problem by the student.

Fifth category: Rhetoric

12. the lr was written with a coherent, clear structure that supported the review.

This category strictly relates to the language domain: the text should be coherent and presented in a logical sequence, regardless of which organizational ( 18 ) approach is chosen. The beginning of each section/subsection should state what themes will be addressed, paragraphs should be carefully linked to each other ( 10 ), and the first sentence of each paragraph should generally summarize the content. Additionally, the student’s statements are clear, sound, and linked to other scholars’ works, and precise and concise language that follows standardized writing conventions (e.g., in terms of active/passive voice and verb tenses) is used. Attention to grammar, such as orthography and punctuation, indicates prudence and supports a robust dissertation/thesis. Ultimately, all of these strategies provide fluency and consistency for the text.

Although the scoring rubric was initially proposed for postgraduate programs in education research, we are convinced that this checklist is a valuable tool for all academic areas. It enables the monitoring of students’ learning curves and a concentrated effort on any criteria that are not yet achieved. For institutions, the checklist is a guide to support supervisors’ feedback, improve students’ writing skills, and highlight the learning goals of each program. These criteria do not form a linear sequence, but ideally, all twelve achievements should be perceived in the LR.

CONCLUSIONS

A single correct method to classify, evaluate and guide the elaboration of an LR has not been established. In this essay, we have suggested directions for planning, structuring and critically evaluating an LR. The planning of the scope of an LR and approaches to complete it is a valuable effort, and the five steps represent a rational starting point. An institutional environment devoted to active learning will support students in continuously reflecting on LRs, which will form a dialogue between the writer and the current literature in a particular field ( 13 ).

The completion of an LR is a challenging and necessary process for understanding one’s own field of expertise. Knowledge is always transitory, but our responsibility as scholars is to provide a critical contribution to our field, allowing others to think through our work. Good researchers are grounded in sophisticated LRs, which reveal a writer’s training and long-lasting academic skills. We recommend using the LR checklist as a tool for strengthening the skills necessary for critical academic writing.

AUTHOR CONTRIBUTIONS

Leite DFB has initially conceived the idea and has written the first draft of this review. Padilha MAS and Cecatti JG have supervised data interpretation and critically reviewed the manuscript. All authors have read the draft and agreed with this submission. Authors are responsible for all aspects of this academic piece.

ACKNOWLEDGMENTS

We are grateful to all of the professors of the ‘Getting Started with Graduate Research and Generic Skills’ module at University College Cork, Cork, Ireland, for suggesting and supporting this article. Funding: DFBL has granted scholarship from Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES) to take part of her Ph.D. studies in Ireland (process number 88881.134512/2016-01). There is no participation from sponsors on authors’ decision to write or to submit this manuscript.

No potential conflict of interest was reported.

1 The questions posed in systematic reviews usually follow the ‘PICOS’ acronym: Population, Intervention, Comparison, Outcomes, Study design.

2 In 1988, Cooper proposed a taxonomy that aims to facilitate students’ and institutions’ understanding of literature reviews. Six characteristics with specific categories are briefly described: Focus: research outcomes, research methodologies, theories, or practices and applications; Goals: integration (generalization, conflict resolution, and linguistic bridge-building), criticism, or identification of central issues; Perspective: neutral representation or espousal of a position; Coverage: exhaustive, exhaustive with selective citations, representative, central or pivotal; Organization: historical, conceptual, or methodological; and Audience: specialized scholars, general scholars, practitioners or policymakers, or the general public.

Literature reviews as independent studies: guidelines for academic practice

  • Original Paper
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  • Published: 14 October 2022
  • Volume 16 , pages 2577–2595, ( 2022 )

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literature review on previous studies

  • Sascha Kraus   ORCID: orcid.org/0000-0003-4886-7482 1 , 2 ,
  • Matthias Breier 3 ,
  • Weng Marc Lim 4 , 8 , 22 ,
  • Marina Dabić 5 , 6 ,
  • Satish Kumar 7 , 8 ,
  • Dominik Kanbach 9 , 10 ,
  • Debmalya Mukherjee 11 ,
  • Vincenzo Corvello 12 ,
  • Juan Piñeiro-Chousa 13 ,
  • Eric Liguori 14 ,
  • Daniel Palacios-Marqués 15 ,
  • Francesco Schiavone 16 , 17 ,
  • Alberto Ferraris 18 , 21 ,
  • Cristina Fernandes 19 , 20 &
  • João J. Ferreira 19  

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Review articles or literature reviews are a critical part of scientific research. While numerous guides on literature reviews exist, these are often limited to the philosophy of review procedures, protocols, and nomenclatures, triggering non-parsimonious reporting and confusion due to overlapping similarities. To address the aforementioned limitations, we adopt a pragmatic approach to demystify and shape the academic practice of conducting literature reviews. We concentrate on the types, focuses, considerations, methods, and contributions of literature reviews as independent, standalone studies. As such, our article serves as an overview that scholars can rely upon to navigate the fundamental elements of literature reviews as standalone and independent studies, without getting entangled in the complexities of review procedures, protocols, and nomenclatures.

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1 Introduction

A literature review – or a review article – is “a study that analyzes and synthesizes an existing body of literature by identifying, challenging, and advancing the building blocks of a theory through an examination of a body (or several bodies) of prior work (Post et al. 2020 , p. 352). Literature reviews as standalone pieces of work may allow researchers to enhance their understanding of prior work in their field, enabling them to more easily identify gaps in the body of literature and potential avenues for future research. More importantly, review articles may challenge established assumptions and norms of a given field or topic, recognize critical problems and factual errors, and stimulate future scientific conversations around that topic. Literature reviews Footnote 1 come in many different formats and purposes:

Some review articles conduct a critical evaluation of the literature, whereas others elect to adopt a more exploratory and descriptive approach.

Some reviews examine data, methodologies, and findings, whereas others look at constructs, themes, and theories.

Some reviews provide summaries by holistically synthesizing the existing research on a topic, whereas others adopt an integrative approach by assessing related and interdisciplinary work.

The number of review articles published as independent or standalone studies has been increasing over time. According to Scopus (i.e., search database ), reviews (i.e., document type ) were first published in journals (i.e., source type ) as independent studies in 1945, and they subsequently appeared in three digits yearly from the late 1980s to the late 1990s, four digits yearly from the early 2000s to the late 2010s, and five digits in the year 2021 (Fig.  1 ). This increase is indicative that reviewers and editors in business and management research alike see value and purpose in review articles to such a level that they are now commonly accepted as independent, standalone studies. This development is also reflected in the fact that some academic journals exclusively publish review articles (e.g., the Academy of Management Annals , or the  International Journal of Management Reviews ), and journals publishing in various fields often have special issues dedicated to literature reviews on certain topic areas (e.g., the Journal of Management and the Journal of International Business Studies ).

figure 1

Full-year publication trend of review articles on Scopus (1945–2021)

One of the most important prerequisites of a high-quality review article is that the work follows an established methodology, systematically selects and analyzes articles, and periodically covers the field to identify latest developments (Snyder 2019 ). Additionally, it needs to be reproducible, well-evidenced, and transparent, resulting in a sample inclusive of all relevant and appropriate studies (Gusenbauer and Haddaway 2020; Hansen et al. 2021 ). This observation is in line with Palmatier et al. ( 2018 ), who state that review articles provide an important synthesis of findings and perspectives in a given body of knowledge. Snyder ( 2019 ) also reaffirmed this rationale, pointing out that review articles have the power to answer research questions beyond that which can be achieved in a single study. Ultimately, readers of review articles stand to gain a one-stop, state-of-the-art synthesis (Lim et al. 2022a ; Popli et al. 2022) that encapsulates critical insights through the process of re-interpreting, re-organizing, and re-connecting a body knowledge (Fan et al. 2022 ).

There are many reasons to conduct review articles. Kraus et al. ( 2020 ) explicitly mention the benefits of conducting systematic reviews by declaring that they often represent the first step in the context of larger research projects, such as doctoral dissertations. When carrying out work of this kind, it is important that a holistic overview of the current state of literature is achieved and embedded into a proper synthesis. This allows researchers to pinpoint relevant research gaps and adequately fit future conceptual or empirical studies into the state of the academic discussion (Kraus et al., 2021 ). A review article as an independent or standalone study is a viable option for any academic – especially young scholars, such as doctoral candidates – who wishes to delve into a specific topic for which a (recent) review article is not available.

The process of conducting a review article can be challenging, especially for novice scholars (Boell and Cecez-Kecmanovic 2015 ). Therefore, it is not surprising that numerous guides have been written in an attempt to improve the quality of review studies and support emerging scholars in their endeavors to have their work published. These guides for conducting review articles span a variety of academic fields, such as engineering education (Borrego et al. 2014 ), health sciences (Cajal et al. 2020 ), psychology (Laher and Hassem 2020 ), supply chain management (Durach et al. 2017 ), or business and entrepreneurship (Kraus et al. 2020 ; Tranfield et al. 2003 ) – the latter were among the first scholars to recognize the need to educate business/management scholars on the roles of review studies in assembling, ascertaining, and assessing the intellectual territory of a specific knowledge domain. Furthermore, they shed light on the stages (i.e., planning the review, conducting the review, reporting, and dissemination) and phases (i.e., identifying the need for a review, preparation of a proposal for a review, development of a review protocol, identification of research, selection of studies, study quality assessment, data extraction and monitoring progress, data synthesis, the report and recommendations, and getting evidence into practice) of conducting a systematic review. Other scholars have either adapted and/or developed new procedures (Kraus et al. 2020 ; Snyder 2019 ) or established review protocols such as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram (Moher et al. 2015 ). The latter provides a checklist that improves transparency and reproducibility, thus reducing questionable research practices. The declarative and procedural knowledge of a checklist allows users to derive value from (and, in some cases, produce) methodological literature reviews.

Two distinct and critical gaps or issues provide impetus for our article. First, while the endeavors of the named scholars are undoubtedly valuable contributions, they often encourage other scholars to explain the methodology of their review studies in a non-parsimonious way ( 1st issue ). This can become problematic if this information distracts and deprives scholars from providing richer review findings, particularly in instances in which publication outlets impose a strict page and/or word limit. More often than not, the early parts (i.e., stages/phases, such as needs, aims, and scope) of these procedures or protocols are explained in the introduction, but they tend to be reiterated in the methodology section due to the prescription of these procedures or protocols. Other parts of these procedures or protocols could also be reported more parsimoniously, for example, by filtering out documents, given that scientific databases (such as Scopus or Web of Science ) have since been upgraded to allow scholars to select and implement filtering criteria when conducting a search (i.e., criterion-by-criterion filtering may no longer be necessary). More often than not, the procedures or protocols of review studies can be signposted (e.g., bracket labeling) and disclosed in a sharp and succinct manner while maintaining transparency and replicability.

Other guides have been written to introduce review nomenclatures (i.e., names/naming) and their equivalent philosophical underpinnings. Palmatier et al. ( 2018 ) introduced three clearly but broadly defined nomenclatures of literature reviews as independent studies: domain-based reviews, theory-based reviews, and method-based reviews. However, such review nomenclatures can be confusing due to their overlapping similarities ( 2nd issue ). For example, Lim et al. ( 2022a ) highlighted their observation that the review nomenclatures associated with domain-based reviews could also be used for theory-based and method-based reviews.

The two aforementioned issues – i.e., the lack of a parsimonious understanding and the reporting of the review methodology , and the confusion emerging from review nomenclatures – are inarguably the unintended outcomes of diving into an advanced (i.e., higher level) understanding of literature review procedures, protocols, and nomenclatures from a philosophical perspective (i.e., underpinnings) without a foundational (i.e., basic level) understanding of the fundamental (i.e., core) elements of literature reviews from a pragmatic perspective. Our article aims to shed light on these issues and hopes to provide clarity for future scholarly endeavors.

Having a foundational understanding of literature reviews as independent studies is (i) necessary when addressing the aforementioned issues; (ii) important in reconciling and scaffolding our understanding, and (iii) relevant and timely due to the proliferation of literature reviews as independent studies. To contribute a solution toward addressing this gap , we aim to demystify review articles as independent studies from a pragmatic standpoint (i.e., practicality). To do so, we deliberately (i) move away from review procedures, protocols, and nomenclatures, and (ii) invest our attention in developing a parsimonious, scaffolded understanding of the fundamental elements (i.e., types, focuses, considerations, methods, and contributions) of review articles as independent studies.

Three contributions distinguish our article. It is worth noting that pragmatic guides (i.e., foundational knowledge), such as the present one, are not at odds with extant philosophical guides (i.e., advanced knowledge), but rather they complement them. Having a foundational knowledge of the fundamental elements of literature reviews as independent studies is valuable , as it can help scholars to (i) gain a good grasp of the fundamental elements of literature reviews as independent studies ( 1st contribution ), and (ii) mindfully adopt or adapt existing review procedures, protocols, and nomenclatures to better suit the circumstances of their reviews (e.g., choosing and developing a well-defined review nomenclature, and choosing and reporting on review considerations and steps more parsimoniously) ( 2nd contribution ). Therefore, this pragmatic guide serves as (iii) a foundational article (i.e., preparatory understanding) for literature reviews as independent studies ( 3rd contribution ). Following this, extant guides using a philosophical approach (i.e., advanced understanding) could be relied upon to make informed review decisions (e.g., adoption, adaptation) in response to the conventions of extant review procedures, protocols, and nomenclatures (Fig.  2 ).

figure 2

Foundational and advanced understanding of literature reviews as independent studies

2 Fundamental elements of literature reviews as independent studies

A foundational understanding of literature reviews as independent studies can be acquired through the appreciation of five fundamental elements – i.e., types, focuses, considerations, methods, and contributions – which are illustrated in Fig.  3 and summarized in the following sections.

figure 3

Fundamental elements of literature reviews as independent studies

There are two types of literature reviews as independent studies: systematic literature reviews ( SLRs ) and non-systematic literature reviews ( non-SLRs ). It is important to recognize that SLRs and non-SLRs are not review nomenclatures (i.e., names/naming) but rather review types (i.e., classifications).

In particular, SLRs are reviews carried out in a systematic way using an adopted or adapted procedure or protocol to guide data curation and analysis, thus enabling transparent disclosure and replicability (Lim et al. 2022a ; Kraus et al. 2020 ). Therefore, any review nomenclature guided by a systematic methodology is essentially an SLR. The origin of this type of literature review can be traced back to the evidence-based medicine movement in the early 1990s, with the objective being to overcome the issue of inconclusive findings in studies for medical treatments (Boell and Cecez-Kecmanovic 2015 ).

In contrast, non-SLRs are reviews conducted without any systematic procedure or protocol; instead, they weave together relevant literature based on the critical evaluations and (subjective) choices of the author(s) through a process of discovery and critique (e.g., pointing out contradictions and questioning assertions or beliefs); they are shaped by the exposure, expertise, and experience (i.e., the “3Es” in judgement calls) of the author(s). Therefore, non-SLRs are essentially critical reviews of the literature (Lim and Weissmann 2021 ).

2.2 Focuses

Unlike Palmatier et al. ( 2018 ) who considered domain-based reviews, theory-based reviews, and method-based reviews as review nomenclatures, we consider domain , theory , and method as three substantive focuses that can take center stage in literature reviews as independent studies. This is in line with our attempt to move away from review nomenclatures when providing a foundational understanding of literature reviews as independent studies.

A review that is domain-focused can examine: (i) a  concept (e.g., customer engagement; Lim et al. 2022b ; digital transformation; Kraus et al. 2021 ; home sharing; Lim et al. 2021 ; sharing economy; Lim 2020 ), (ii) a context (e.g., India; Mukherjee et al. 2022a ), (iii) a discipline (e.g., entrepreneurship; Ferreira et al. 2015 ; international business; Ghauri et al. 2021 ), (iv) a field (e.g., family business; Lahiri et al. 2020 ; Rovelli et al. 2021 ; female entrepreneurship; Ojong et al. 2021 ), or (v) an outlet (e.g., Journal of Business Research ; Donthu et al. 2020 ; Management International Review ; Mukherjee et al. 2021 ; Review of Managerial Science ; Mas-Tur et al. 2020 ), which typically offer broad, overarching insights.

Domain-focused hybrids , such as the between-domain hybrid (e.g., concept-discipline hybrid, such as digital transformation in business and management; Kraus et al. 2022 ; religion in business and entrepreneurship; Kumar et al. 2022a ; personality traits in entrepreneurship; Salmony and Kanbach 2022 ; and policy implications in HR and OB research; Aguinis et al., 2022 ) and the within-domain hybrid (e.g., the concept-concept hybrid, such as customer engagement and social media; Lim and Rasul 2022 ; and global business and organizational excellence; Lim 2022 ; and the discipline-discipline hybrid, such as neuromarketing; Lim 2018 ) are also common as they can provide finer-grained insights.

A review that is theory-focused can explore a standalone theory (e.g., theory of planned behavior; Duan and Jiang 2008 ), as well as a theory in conjunction with a domain , such as the concept-theory hybrid (e.g., behavioral control and theory of planned behavior; Lim and Weissmann 2021 ) and the theory-discipline hybrid (e.g., theory of planned behavior in hospitality, leisure, and tourism; Ulker-Demirel and Ciftci 2020 ), or a theory in conjunction with a method (e.g., theory of planned behavior and structural equation modeling).

A review that is method-focused can investigate a standalone method (e.g., structural equation modeling; Deng et al. 2018 ) or a method in conjunction with a domain , such as the method-discipline hybrid (e.g., fsQCA in business and management; Kumar et al. 2022b ).

2.3 Planning the review, critical considerations, and data collection

The considerations required for literature reviews as independent studies depend on their type: SLRs or non-SLRs.

For non-SLRs, scholars often rely on the 3Es (i.e., exposure, expertise, and experience) to provide a critical review of the literature. Scholars who embark on non-SLRs should be well versed with the literature they are dealing with. They should know the state of the literature (e.g., debatable, underexplored, and well-established knowledge areas) and how it needs to be deciphered (e.g., tenets and issues) and approached (e.g., reconciliation proposals and new pathways) to advance theory and practice. In this regard, non-SLRs follow a deductive reasoning approach, whereby scholars initially develop a set of coverage areas for reviewing a domain, theory, or method and subsequently draw on relevant literature to shed light and support scholarly contentions in each area.

For SLRs, scholars often rely on a set of criteria to provide a well-scoped (i.e., breadth and depth), structured (i.e., organized aspects), integrated (i.e., synthesized evidence) and interpreted/narrated (i.e., describing what has happened, how and why) systematic review of the literature. Footnote 2 In this regard, SLRs follow an inductive reasoning approach, whereby a set of criteria is established and implemented to develop a corpus of scholarly documents that scholars can review. They can then deliver a state-of-the-art overview, as well as a future agenda for a domain, theory, or method. Such criteria are often listed in philosophical guides on SLR procedures (e.g., Kraus et al. 2020 ; Snyder 2019 ) and protocols (e.g., PRISMA), and they may be adopted/adapted with justifications Footnote 3 . Based on their commonalities they can be summarized as follows:

Search database (e.g., “Scopus” and/or “Web of Science”) can be defined based on justified evidence (e.g., by the two being the largest scientific databases of scholarly articles that can provide on-demand bibliographic data or records; Pranckutė 2021 ). To avoid biased outcomes due to the scope covered by the selected database, researchers could utilize two or more different databases (Dabić et al. 2021 ).

Search keywords may be developed by reading scholarly documents and subsequently brainstorming with experts. The expanding number of databases, journals, periodicals, automated approaches, and semi-automated procedures that use text mining and machine learning can offer researchers the ability to source new, relevant research and forecast the citations of influential studies. This enables them to determine further relevant articles.

Boolean operators (e.g., AND, OR) should be strategically used in developing the  string   of search keywords (e.g., “engagement” AND “customer” OR “consumer” OR “business”). Furthermore, the correct and precise application of quotation marks is important but is very frequently sidestepped, resulting in incorrect selection processes and differentiated results.

Search period (e.g., between a specified period [e.g., 2000 to 2020] or up to the latest full year at the time or writing [e.g., up to 2021]) can be defined based on the justified scope of study (e.g., contemporary evolution versus historical trajectory).

Search field (e.g., “article title, abstract, keywords”) can be defined based on justified assumptions (e.g., it is assumed that the focus of relevant documents will be mentioned in the article title, abstract, and/or keywords).

Subject area (e.g., “business, management, and accounting”) can be defined based on justified principles (e.g., the focus of the review is on the marketing discipline, which is located under the “business, management, and accounting” subject area in Scopus).

Publication stage (e.g., “final”) can be defined based on justified grounds (e.g., enabling greater accuracy in replication).

Document type (e.g., “article” and/or “review”), which reflects the type of scientific/practical contributions (e.g., empirical, synthesis, thought), can be defined based on justified rationales (e.g., articles selected because they are peer-reviewed; editorials not selected because they are not peer-reviewed).

Source type (e.g., “journal”) can be defined based on justified reasons (e.g., journals selected because they publish finalized work; conference proceedings not selected because they are work in progress, and in business/management, they are usually not being considered as full-fledged “publications”).

Language (e.g., “English”) can be determined based on justified limitations (e.g., nowadays, there are not many reasons to use another language besides the academic lingua franca English). Different spellings should also be considered, as the literature may contain both American and British spelling variants (e.g., organization and organisation). Truncation and wildcards in searches are recommended to capture both sets of spellings. It is important to note that each database varies in its symbology.

Quality filtering (e.g., “A*” and “A” or “4*”, “4”, and “3”) can be defined based on justified motivations (e.g., the goal is to unpack the most originally and rigorously produced knowledge, which is the hallmark of premier journals, such as those ranked “A*” and “A” by the Australian Business Deans Council [ABDC] Journal Quality List [JQL] and rated “4*”, “4”, and “3” by the Chartered Association of Business Schools [CABS] Academic Journal Guide [AJG]).

Document relevance (i.e., within the focus of the review) can be defined based on justified judgement (e.g., for a review focusing on customer engagement, articles that mention customer engagement as a passing remark without actually investigating it would be excluded).

Others: Screening process should be accomplished by beginning with the deduction of duplicate results from other databases, tracked using abstract screening to exclude unfitting studies, and ending with the full-text screening of the remaining documents.

Others: Exclusion-inclusion criteria interpretation of the abstracts/articles is obligatory when deciding whether or not the articles dealt with the matter. This step could involve removing a huge percentage of initially recognized articles.

Others: Codebook building pertains to the development of a codebook of the main descriptors within a specific field. An inductive approach can be followed and, in this case, descriptors are not established beforehand. Instead, they are established through the analysis of the articles’ content. This procedure is made up of several stages: (i) the extraction of important content from titles, abstracts, and keywords; (ii) the classification of this content to form a reduced list of the core descriptors; and (iii) revising the codebook in iterations and combining similar categories, thus developing a short list of descriptors (López-Duarte et al. 2016 , p. 512; Dabić et al. 2015 ; Vlacic et al. 2021 ).

2.4 Methods

Various methods are used to analyze the pertinent literature. Often, scholars choose a method for corpus analysis before corpus curation. Knowing the analytical technique beforehand is useful, as it allows researchers to acquire and prepare the right data in the right format. This typically occurs when scholars have decided upon and justified pursuing a specific review nomenclature upfront (e.g., bibliometric reviews) based on the problem at hand (e.g., broad domain [outlet] with a large corpus [thousands of articles], such as a premier journal that has been publishing for decades) (Donthu et al. 2021 ). However, this may not be applicable in instances where (i) scholars do not curate a corpus of articles (non-SLRs), and (ii) scholars only know the size of the corpus of articles once that corpus is curated (SLRs). Therefore, scholars may wish to decide on a method of analyzing the literature depending on (i) whether they rely on a corpus of articles (i.e., yes or no), and (ii) the size of the corpus of articles that they rely on to review the literature (i.e., n  = 0 to ∞).

When analytical techniques (e.g., bibliometric analysis, critical analysis, meta-analysis) are decoupled from review nomenclatures (e.g., bibliometric reviews, critical reviews, meta-analytical reviews), we uncover a toolbox of the following methods for use when analyzing the literature:

Bibliometric analysis measures the literature and processes data by using algorithm, arithmetic, and statistics to analyze, explore, organize, and investigate large amounts of data. This enables scholars to identify and recognize potential “hidden patterns” that could help them during the literature review process. Bibliometrics allows scholars to objectively analyze a large corpus of articles (e.g., high hundreds or more) using quantitative techniques (Donthu et al. 2021 ). There are two overarching categories for bibliometric analysis: performance analysis and science mapping. Performance analysis enables scholars to assess the productivity (publication) and impact (citation) of the literature relating to a domain, method, or theory using various quantitative metrics (e.g., average citations per publication or year, h -index, g -index, i -index). Science mapping grants scholars the ability to map the literature in that domain, method, or theory based on bibliographic data (e.g., bibliographic coupling generates thematic clusters based on similarities in shared bibliographic data [e.g., references] among citing articles; co-citation analysis generates thematic clusters based on commonly cited articles; co-occurrence analysis generates thematic clusters based on bibliographic data [e.g., keywords] that commonly appear together; PageRank analysis generates thematic clusters based on articles that are commonly cited in highly cited articles; and topic modeling generates thematic clusters based on the natural language processing of bibliographic data [e.g., article title, abstract, and keywords]). Footnote 4 Given the advancement in algorithms and technology, reviews using bibliometric analysis are considered to be smart (Kraus et al. 2021 ) and technologically-empowered (Kumar et al. 2022b ) SLRs, in which a review has harnessed the benefits of (i) the machine learning of the bibliographic data of scholarly research from technologically-empowered scientific databases, and (ii) big data analytics involving various science mapping techniques (Kumar et al. 2022c ).

Content analysis allows scholars to analyze a small to medium corpus of articles (i.e., tens to low hundreds) using quantitative and qualitative techniques. From a quantitative perspective , scholars can objectively carry out a content analysis by quantifying a specific unit of analysis . A useful method of doing so involves adopting, adapting, or developing an organizing framework . For example, Lim et al. ( 2021 ) employed an organizing (ADO-TCM) framework to quantify content in academic literature based on: (i) the categories of knowledge; (ii) the relationships between antecedents, decisions, and outcomes; and (iii) the theories, contexts, and methods used to develop the understanding for (i) and (ii). The rapid evolution of software for content analysis allows scholars to carry out complex elaborations on the corpus of analyzed articles, so much so that the most recent software enables the semi-automatic development of an organizing framework (Ammirato et al. 2022 ). From a qualitative perspective , scholars can conduct a content analysis or, more specifically, a thematic analysis , by subjectively organizing the content into themes. For example, Creevey et al. ( 2022 ) reviewed the literature on social media and luxury, providing insights on five core themes (i.e., luxury brand strategy, luxury brand social media communications, luxury consumer attitudes and perceptions, engagement, and the influence of social media on brand performance-related outcomes) generated through a content (thematic) analysis. Systematic approaches for inductive concept development through qualitative research are similarly applied in literature reviews in an attempt to reduce the subjectivity of derived themes. Following the principles of the approach by Gioia et al. ( 2012 ), Korherr and Kanbach ( 2021 ) develop a taxonomy of human-related capabilities in big data analytics. Building on a sample of 75 studies for the literature review, 33 first-order concepts are identified. These are categorized into 15 second-order themes and are finally merged into five aggregate dimensions. Using the same procedure, Leemann and Kanbach ( 2022 ) identify 240 idiosyncratic dynamic capabilities in a sample of 34 studies for their literature review. They then categorize these into 19 dynamic sub-capabilities. The advancement of technology also makes it possible to conduct content analysis using computer assisted qualitative data analysis (CAQDA) software (e.g., ATLAS.ti, Nvivo, Quirkos) (Lim et al. 2022a ).

Critical analysis allows scholars to subjectively use their 3Es (i.e., exposure, expertise, and experience) to provide a critical evaluation of academic literature. This analysis is typically used in non-SLRs, and can be deployed in tandem with other analyses, such as bibliometric analysis and content analysis in SLRs, which are used to discuss consensual, contradictory, and underexplored areas of the literature. For SLRs, scholars are encouraged to engage in critical evaluations of the literature so that they can truly contribute to advancing theory and practice (Baker et al. 2022 ; Lim et al. 2022a ; Mukherjee et al. 2022b ).

Meta-analysis allows scholars to objectively establish a quantitative estimate of commonly studied relationships in the literature (Grewal et al. 2018 ). This analysis is typically employed in SLRs intending to reconcile a myriad of relationships (Lim et al. 2022a ). The relationships established are often made up of conflicting evidence (e.g., a positive or significant effect in one study, but a negative or non-significant effect in another study). However, through meta-analysis, scholars are able to identify potential factors (e.g., contexts or sociodemographic information) that may have led to the conflict.

Others: Multiple correspondence analysis helps to map the field, assessing the associations between qualitative content within a matrix of variables and cases. Homogeneity Analysis by Means of Alternating Least Squares ( HOMALS ) is also considered useful in allowing researchers to map out the intellectual structure of a variety of research fields (Gonzalez-Loureiro et al. 2015 ; Gonzalez-Louriero 2021; Obradović et al. 2021 ). HOMALS can be performed in R or used along with a matrix through SPSS software. In summary, the overall objective of this analysis is to discover a low dimensional representation of the original high dimensional space (i.e., the matrix of descriptors and articles). To measure the goodness of fit, a loss function is used. This function is used minimally, and the HOMALS algorithm is applied to the least squares loss functions in SPSS. This analysis provides a proximity map, in which articles and descriptors are shown in low-dimensional spaces (typically on two axes). Keywords are paired and each couple that appears together in a large number of articles is shown to be closer on the map and vice-versa.

When conducting a literature review, software solutions allow researchers to cover a broad range of variables, from built-in functions of statistical software packages to software orientated towards meta-analyses, and from commercial to open-source solutions. Personal preference plays a huge role, but the decision as to which software will be the most useful is entirely dependent on how complex the methods and the dataset are. Of all the commercial software providers, we have found the built-in functions of (i) R and VOSviewer most useful in performing bibliometric analysis (Aria and Cuccurullo 2017 ; R Core Team 2021 ; Van Eck and Waltman 2014 ) and (ii) Stata most useful in performing meta-analytical tasks.

Many different analytical tools have been used. These include simple document counting, citation analysis, word frequency analysis, cluster analysis, co-word analysis, and cooperation analysis (Daim et al. 2006 ). Software has also been produced for bibliometric analysis, such as the Thomson Data Analyzer (TDA), which Thomson Reuters created, and CiteSpace developed by Chen ( 2013 ). VOSviewer helps us to construct and visualize bibliometric networks, which can include articles, journals, authors, countries, and institutions, among others (Van Eck and Waltman 2014 ). These can be organized based on citations, co-citations, bibliographic coupling, or co-authorship relations. In addition, VOSviewer provides text mining functions, which can be used to facilitate a better understanding of co-occurrence networks with regards to the key terms taken from a body of scientific literature (Donthu et al. 2021 ; Wong 2018 ). Other frequently used tools include for bibliometric analysis include Bibliometrix/Biblioshiny in R, CitNetExplorer, and Gephi, among others.

2.5 Contributions

Well-conducted literature reviews may make multiple contributions to the literature as standalone, independent studies.

Generally, there are three primary contributions of literature reviews as independent studies: (i) to provide an overview of current knowledge in the domain, method, or theory, (ii) to provide an evaluation of knowledge progression in the domain, method, or theory, including the establishment of key knowledge, conflicting or inconclusive findings, and emerging and underexplored areas, and (iii) to provide a proposal for potential pathways for advancing knowledge in the domain, method, or theory (Lim et al. 2022a , p. 487). Developing theory through literature reviews can take many forms, including organizing and categorizing the literature, problematizing the literature, identifying and exposing contradictions, developing analogies and metaphors, and setting out new narratives and conceptualizations (Breslin and Gatrell 2020 ). Taken collectively, these contributions offer crystalized, evidence-based insights that both ‘mine’ and ‘prospect’ the literature, highlighting extant gaps and how they can be resolved (e.g., flags paradoxes or theoretical tensions, explaining why something has not been done, what the challenges are, and how these challenges can be overcome). These contributions can be derived through successful bibliometric analysis, content analysis, critical analysis, and meta-analysis.

Additionally, the deployment of specific methods can bring in further added value. For example, a performance analysis in a bibliometric analysis can contribute to: (i) objectively assessing and reporting research productivity and impact ; (ii) ascertaining reach for coverage claims ; (iii) identifying social dominance and hidden biases ; (iv) detecting anomalies ; and (v) evaluating ( equitable ) relative performance ; whereas science mapping in bibliometric analysis can contribute to: (i) objectively discovering thematic clusters of knowledge ; (ii) clarifying nomological networks ; (iii) mapping social patterns ; (iv) tracking evolutionary nuances ; and (v) recognizing knowledge gaps (Mukherjee et al. 2022b , p. 105).

3 Conclusion

Independent literature reviews will continue to be written as a result of their necessity, importance, relevance, and urgency when it comes to advancing knowledge (Lim et al. 2022a ; Mukherjee et al. 2022b ), and this can be seen in the increasing number of reviews being published over the last several years. Literature reviews advance academic discussion. Journal publications on various topics and subject areas are becoming more frequent sites for publication. This trend will only heighten the need for literature reviews. This article offers directions and control points that address the needs of three different stakeholder groups: producers (i.e., potential authors), evaluators (i.e., journal editors and reviewers), and users (i.e., new researchers looking to learn more about a particular methodological issue, and those teaching the next generation of scholars). Future producers will derive value from this article’s teachings on the different fundamental elements and methodological nuances of literature reviews. Procedural knowledge (i.e., using control points to assist in decision-making during the manuscript preparation phase) will also be of use. Evaluators will be able to make use of the procedural and declarative knowledge evident in control points as well. As previously outlined, the need to cultivate novelty within research on business and management practices is vital. Scholars must also be supported to choose not only safe mining approaches; they should also be encouraged to attempt more challenging and risky ventures. It is important to note that abstracts often seem to offer a lot of potential, stating that authors intend to make large conceptual contributions, broadening the horizons of the field.

Our article offers important insights also for practitioners. Noteworthily, our framework can support corporate managers in decomposing and better understanding literature reviews as ad-hoc and independent studies about specific topics that matter for their organization. For instance, practitioners can understand more easily what are the emerging trends within their domain of interest and make corporate decisions in line with such trends.

This article arises from an intentional decoupling from philosophy, in favor of adopting a more pragmatic approach. This approach can assist us in clarifying the fundamental elements of literature reviews as independent studies. Five fundamental elements must be considered: types, focuses, considerations, methods, and contributions. These elements offer a useful frame for scholars starting to work on a literature review. Overview articles (guides) such as ours are thus invaluable, as they equip scholars with a solid foundational understanding of the integral elements of a literature review. Scholars can then put these teachings into practice, armed with a better understanding of the philosophy that underpins the procedures, protocols, and nomenclatures of literature reviews as independent studies.

Data availability

Our manuscript has no associate data.

Our focus here is on standalone literature reviews in contrast with literature reviews that form the theoretical foundation for a research article.

Scoping reviews, structured reviews, integrative reviews, and interpretive/narrative reviews are commonly found in review nomenclature. However, the philosophy of these review nomenclatures essentially reflects what constitutes a good SLR. That is to say, a good SLR should be well scoped, structured, integrated, and interpreted/narrated. This observation reaffirms our position and the value of moving away from review nomenclatures to gain a foundational understanding of literature reviews as independent studies.

Given that many of these considerations can be implemented simultaneously in contemporary versions of scientific databases, scholars may choose to consolidate them into a single (or a few) step(s), where appropriate, so that they can be reported more parsimoniously. For a parsimonious but transparent and replicable exemplar, see Lim ( 2022 ).

Where keywords are present (e.g., author keywords or keywords derived from machine learning [e.g., natural language processing]), it is assumed that each keyword represents a specific meaning (e.g., topic [concept, context], method), and that a collection of keywords grouped under the same cluster represents a specific theme.

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Sascha Kraus

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Kraus, S., Breier, M., Lim, W.M. et al. Literature reviews as independent studies: guidelines for academic practice. Rev Manag Sci 16 , 2577–2595 (2022). https://doi.org/10.1007/s11846-022-00588-8

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Literature Review: The What, Why and How-to Guide — Introduction

  • Getting Started
  • How to Pick a Topic
  • Strategies to Find Sources
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What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

  • To develop a theory or evaluate an existing theory
  • To summarize the historical or existing state of a research topic
  • Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

  • A research paper assigned in a course
  • A thesis or dissertation
  • A grant proposal
  • An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

  • Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

  • Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

  • Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

  • Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

  • UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
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Research Methods

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Literature Review

  • What is a Literature Review?
  • What is NOT a Literature Review?
  • Purposes of a Literature Review
  • Types of Literature Reviews
  • Literature Reviews vs. Systematic Reviews
  • Systematic vs. Meta-Analysis

Literature Review  is a comprehensive survey of the works published in a particular field of study or line of research, usually over a specific period of time, in the form of an in-depth, critical bibliographic essay or annotated list in which attention is drawn to the most significant works.

Also, we can define a literature review as the collected body of scholarly works related to a topic:

  • Summarizes and analyzes previous research relevant to a topic
  • Includes scholarly books and articles published in academic journals
  • Can be an specific scholarly paper or a section in a research paper

The objective of a Literature Review is to find previous published scholarly works relevant to an specific topic

  • Help gather ideas or information
  • Keep up to date in current trends and findings
  • Help develop new questions

A literature review is important because it:

  • Explains the background of research on a topic.
  • Demonstrates why a topic is significant to a subject area.
  • Helps focus your own research questions or problems
  • Discovers relationships between research studies/ideas.
  • Suggests unexplored ideas or populations
  • Identifies major themes, concepts, and researchers on a topic.
  • Tests assumptions; may help counter preconceived ideas and remove unconscious bias.
  • Identifies critical gaps, points of disagreement, or potentially flawed methodology or theoretical approaches.
  • Indicates potential directions for future research.

All content in this section is from Literature Review Research from Old Dominion University 

Keep in mind the following, a literature review is NOT:

Not an essay 

Not an annotated bibliography  in which you summarize each article that you have reviewed.  A literature review goes beyond basic summarizing to focus on the critical analysis of the reviewed works and their relationship to your research question.

Not a research paper   where you select resources to support one side of an issue versus another.  A lit review should explain and consider all sides of an argument in order to avoid bias, and areas of agreement and disagreement should be highlighted.

A literature review serves several purposes. For example, it

  • provides thorough knowledge of previous studies; introduces seminal works.
  • helps focus one’s own research topic.
  • identifies a conceptual framework for one’s own research questions or problems; indicates potential directions for future research.
  • suggests previously unused or underused methodologies, designs, quantitative and qualitative strategies.
  • identifies gaps in previous studies; identifies flawed methodologies and/or theoretical approaches; avoids replication of mistakes.
  • helps the researcher avoid repetition of earlier research.
  • suggests unexplored populations.
  • determines whether past studies agree or disagree; identifies controversy in the literature.
  • tests assumptions; may help counter preconceived ideas and remove unconscious bias.

As Kennedy (2007) notes*, it is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the original studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally that become part of the lore of field. In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews.

Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are several approaches to how they can be done, depending upon the type of analysis underpinning your study. Listed below are definitions of types of literature reviews:

Argumentative Review      This form examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to to make summary claims of the sort found in systematic reviews.

Integrative Review      Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication.

Historical Review      Few things rest in isolation from historical precedent. Historical reviews are focused on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review      A review does not always focus on what someone said [content], but how they said it [method of analysis]. This approach provides a framework of understanding at different levels (i.e. those of theory, substantive fields, research approaches and data collection and analysis techniques), enables researchers to draw on a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection and data analysis, and helps highlight many ethical issues which we should be aware of and consider as we go through our study.

Systematic Review      This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyse data from the studies that are included in the review. Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?"

Theoretical Review      The purpose of this form is to concretely examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review help establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

* Kennedy, Mary M. "Defining a Literature."  Educational Researcher  36 (April 2007): 139-147.

All content in this section is from The Literature Review created by Dr. Robert Larabee USC

Robinson, P. and Lowe, J. (2015),  Literature reviews vs systematic reviews.  Australian and New Zealand Journal of Public Health, 39: 103-103. doi: 10.1111/1753-6405.12393

literature review on previous studies

What's in the name? The difference between a Systematic Review and a Literature Review, and why it matters . By Lynn Kysh from University of Southern California

Diagram for "What's in the name? The difference between a Systematic Review and a Literature Review, and why it matters"

Systematic review or meta-analysis?

A  systematic review  answers a defined research question by collecting and summarizing all empirical evidence that fits pre-specified eligibility criteria.

A  meta-analysis  is the use of statistical methods to summarize the results of these studies.

Systematic reviews, just like other research articles, can be of varying quality. They are a significant piece of work (the Centre for Reviews and Dissemination at York estimates that a team will take 9-24 months), and to be useful to other researchers and practitioners they should have:

  • clearly stated objectives with pre-defined eligibility criteria for studies
  • explicit, reproducible methodology
  • a systematic search that attempts to identify all studies
  • assessment of the validity of the findings of the included studies (e.g. risk of bias)
  • systematic presentation, and synthesis, of the characteristics and findings of the included studies

Not all systematic reviews contain meta-analysis. 

Meta-analysis is the use of statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review.  More information on meta-analyses can be found in  Cochrane Handbook, Chapter 9 .

A meta-analysis goes beyond critique and integration and conducts secondary statistical analysis on the outcomes of similar studies.  It is a systematic review that uses quantitative methods to synthesize and summarize the results.

An advantage of a meta-analysis is the ability to be completely objective in evaluating research findings.  Not all topics, however, have sufficient research evidence to allow a meta-analysis to be conducted.  In that case, an integrative review is an appropriate strategy. 

Some of the content in this section is from Systematic reviews and meta-analyses: step by step guide created by Kate McAllister.

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literature review on previous studies

What Is A Literature Review?

A plain-language explainer (with examples).

By:  Derek Jansen (MBA) & Kerryn Warren (PhD) | June 2020 (Updated May 2023)

If you’re faced with writing a dissertation or thesis, chances are you’ve encountered the term “literature review” . If you’re on this page, you’re probably not 100% what the literature review is all about. The good news is that you’ve come to the right place.

Literature Review 101

  • What (exactly) is a literature review
  • What’s the purpose of the literature review chapter
  • How to find high-quality resources
  • How to structure your literature review chapter
  • Example of an actual literature review

What is a literature review?

The word “literature review” can refer to two related things that are part of the broader literature review process. The first is the task of  reviewing the literature  – i.e. sourcing and reading through the existing research relating to your research topic. The second is the  actual chapter  that you write up in your dissertation, thesis or research project. Let’s look at each of them:

Reviewing the literature

The first step of any literature review is to hunt down and  read through the existing research  that’s relevant to your research topic. To do this, you’ll use a combination of tools (we’ll discuss some of these later) to find journal articles, books, ebooks, research reports, dissertations, theses and any other credible sources of information that relate to your topic. You’ll then  summarise and catalogue these  for easy reference when you write up your literature review chapter. 

The literature review chapter

The second step of the literature review is to write the actual literature review chapter (this is usually the second chapter in a typical dissertation or thesis structure ). At the simplest level, the literature review chapter is an  overview of the key literature  that’s relevant to your research topic. This chapter should provide a smooth-flowing discussion of what research has already been done, what is known, what is unknown and what is contested in relation to your research topic. So, you can think of it as an  integrated review of the state of knowledge  around your research topic. 

Starting point for the literature review

What’s the purpose of a literature review?

The literature review chapter has a few important functions within your dissertation, thesis or research project. Let’s take a look at these:

Purpose #1 – Demonstrate your topic knowledge

The first function of the literature review chapter is, quite simply, to show the reader (or marker) that you  know what you’re talking about . In other words, a good literature review chapter demonstrates that you’ve read the relevant existing research and understand what’s going on – who’s said what, what’s agreed upon, disagreed upon and so on. This needs to be  more than just a summary  of who said what – it needs to integrate the existing research to  show how it all fits together  and what’s missing (which leads us to purpose #2, next). 

Purpose #2 – Reveal the research gap that you’ll fill

The second function of the literature review chapter is to  show what’s currently missing  from the existing research, to lay the foundation for your own research topic. In other words, your literature review chapter needs to show that there are currently “missing pieces” in terms of the bigger puzzle, and that  your study will fill one of those research gaps . By doing this, you are showing that your research topic is original and will help contribute to the body of knowledge. In other words, the literature review helps justify your research topic.  

Purpose #3 – Lay the foundation for your conceptual framework

The third function of the literature review is to form the  basis for a conceptual framework . Not every research topic will necessarily have a conceptual framework, but if your topic does require one, it needs to be rooted in your literature review. 

For example, let’s say your research aims to identify the drivers of a certain outcome – the factors which contribute to burnout in office workers. In this case, you’d likely develop a conceptual framework which details the potential factors (e.g. long hours, excessive stress, etc), as well as the outcome (burnout). Those factors would need to emerge from the literature review chapter – they can’t just come from your gut! 

So, in this case, the literature review chapter would uncover each of the potential factors (based on previous studies about burnout), which would then be modelled into a framework. 

Purpose #4 – To inform your methodology

The fourth function of the literature review is to  inform the choice of methodology  for your own research. As we’ve  discussed on the Grad Coach blog , your choice of methodology will be heavily influenced by your research aims, objectives and questions . Given that you’ll be reviewing studies covering a topic close to yours, it makes sense that you could learn a lot from their (well-considered) methodologies.

So, when you’re reviewing the literature, you’ll need to  pay close attention to the research design , methodology and methods used in similar studies, and use these to inform your methodology. Quite often, you’ll be able to  “borrow” from previous studies . This is especially true for quantitative studies , as you can use previously tried and tested measures and scales. 

Free Webinar: Literature Review 101

How do I find articles for my literature review?

Finding quality journal articles is essential to crafting a rock-solid literature review. As you probably already know, not all research is created equally, and so you need to make sure that your literature review is  built on credible research . 

We could write an entire post on how to find quality literature (actually, we have ), but a good starting point is Google Scholar . Google Scholar is essentially the academic equivalent of Google, using Google’s powerful search capabilities to find relevant journal articles and reports. It certainly doesn’t cover every possible resource, but it’s a very useful way to get started on your literature review journey, as it will very quickly give you a good indication of what the  most popular pieces of research  are in your field.

One downside of Google Scholar is that it’s merely a search engine – that is, it lists the articles, but oftentimes  it doesn’t host the articles . So you’ll often hit a paywall when clicking through to journal websites. 

Thankfully, your university should provide you with access to their library, so you can find the article titles using Google Scholar and then search for them by name in your university’s online library. Your university may also provide you with access to  ResearchGate , which is another great source for existing research. 

Remember, the correct search keywords will be super important to get the right information from the start. So, pay close attention to the keywords used in the journal articles you read and use those keywords to search for more articles. If you can’t find a spoon in the kitchen, you haven’t looked in the right drawer. 

Need a helping hand?

literature review on previous studies

How should I structure my literature review?

Unfortunately, there’s no generic universal answer for this one. The structure of your literature review will depend largely on your topic area and your research aims and objectives.

You could potentially structure your literature review chapter according to theme, group, variables , chronologically or per concepts in your field of research. We explain the main approaches to structuring your literature review here . You can also download a copy of our free literature review template to help you establish an initial structure.

In general, it’s also a good idea to start wide (i.e. the big-picture-level) and then narrow down, ending your literature review close to your research questions . However, there’s no universal one “right way” to structure your literature review. The most important thing is not to discuss your sources one after the other like a list – as we touched on earlier, your literature review needs to synthesise the research , not summarise it .

Ultimately, you need to craft your literature review so that it conveys the most important information effectively – it needs to tell a logical story in a digestible way. It’s no use starting off with highly technical terms and then only explaining what these terms mean later. Always assume your reader is not a subject matter expert and hold their hand through a journe y of the literature while keeping the functions of the literature review chapter (which we discussed earlier) front of mind.

A good literature review should synthesise the existing research in relation to the research aims, not simply summarise it.

Example of a literature review

In the video below, we walk you through a high-quality literature review from a dissertation that earned full distinction. This will give you a clearer view of what a strong literature review looks like in practice and hopefully provide some inspiration for your own. 

Wrapping Up

In this post, we’ve (hopefully) answered the question, “ what is a literature review? “. We’ve also considered the purpose and functions of the literature review, as well as how to find literature and how to structure the literature review chapter. If you’re keen to learn more, check out the literature review section of the Grad Coach blog , as well as our detailed video post covering how to write a literature review . 

Literature Review Course

Psst… there’s more!

This post is an extract from our bestselling short course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

16 Comments

BECKY NAMULI

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Derek Jansen

Thanks for the kind words, Becky. Good luck with your literature review 🙂

ELaine

This website is amazing, it really helps break everything down. Thank you, I would have been lost without it.

Timothy T. Chol

This is review is amazing. I benefited from it a lot and hope others visiting this website will benefit too.

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Tahir

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Rosalind Whitworth

This was so useful. Thank you so much.

hassan sakaba

Hi, Concept was explained nicely by both of you. Thanks a lot for sharing it. It will surely help research scholars to start their Research Journey.

Susan

The review is really helpful to me especially during this period of covid-19 pandemic when most universities in my country only offer online classes. Great stuff

Mohamed

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Mayoga Patrick

So helpful to me as a student

Amr E. Hassabo

GradCoach is a fantastic site with brilliant and modern minds behind it.. I spent weeks decoding the substantial academic Jargon and grounding my initial steps on the research process, which could be shortened to a couple of days through the Gradcoach. Thanks again!

S. H Bawa

This is an amazing talk. I paved way for myself as a researcher. Thank you GradCoach!

Carol

Well-presented overview of the literature!

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This was brilliant. So clear. Thank you

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Research Method

Home » Literature Review – Types Writing Guide and Examples

Literature Review – Types Writing Guide and Examples

Table of Contents

Literature Review

Literature Review

Definition:

A literature review is a comprehensive and critical analysis of the existing literature on a particular topic or research question. It involves identifying, evaluating, and synthesizing relevant literature, including scholarly articles, books, and other sources, to provide a summary and critical assessment of what is known about the topic.

Types of Literature Review

Types of Literature Review are as follows:

  • Narrative literature review : This type of review involves a comprehensive summary and critical analysis of the available literature on a particular topic or research question. It is often used as an introductory section of a research paper.
  • Systematic literature review: This is a rigorous and structured review that follows a pre-defined protocol to identify, evaluate, and synthesize all relevant studies on a specific research question. It is often used in evidence-based practice and systematic reviews.
  • Meta-analysis: This is a quantitative review that uses statistical methods to combine data from multiple studies to derive a summary effect size. It provides a more precise estimate of the overall effect than any individual study.
  • Scoping review: This is a preliminary review that aims to map the existing literature on a broad topic area to identify research gaps and areas for further investigation.
  • Critical literature review : This type of review evaluates the strengths and weaknesses of the existing literature on a particular topic or research question. It aims to provide a critical analysis of the literature and identify areas where further research is needed.
  • Conceptual literature review: This review synthesizes and integrates theories and concepts from multiple sources to provide a new perspective on a particular topic. It aims to provide a theoretical framework for understanding a particular research question.
  • Rapid literature review: This is a quick review that provides a snapshot of the current state of knowledge on a specific research question or topic. It is often used when time and resources are limited.
  • Thematic literature review : This review identifies and analyzes common themes and patterns across a body of literature on a particular topic. It aims to provide a comprehensive overview of the literature and identify key themes and concepts.
  • Realist literature review: This review is often used in social science research and aims to identify how and why certain interventions work in certain contexts. It takes into account the context and complexities of real-world situations.
  • State-of-the-art literature review : This type of review provides an overview of the current state of knowledge in a particular field, highlighting the most recent and relevant research. It is often used in fields where knowledge is rapidly evolving, such as technology or medicine.
  • Integrative literature review: This type of review synthesizes and integrates findings from multiple studies on a particular topic to identify patterns, themes, and gaps in the literature. It aims to provide a comprehensive understanding of the current state of knowledge on a particular topic.
  • Umbrella literature review : This review is used to provide a broad overview of a large and diverse body of literature on a particular topic. It aims to identify common themes and patterns across different areas of research.
  • Historical literature review: This type of review examines the historical development of research on a particular topic or research question. It aims to provide a historical context for understanding the current state of knowledge on a particular topic.
  • Problem-oriented literature review : This review focuses on a specific problem or issue and examines the literature to identify potential solutions or interventions. It aims to provide practical recommendations for addressing a particular problem or issue.
  • Mixed-methods literature review : This type of review combines quantitative and qualitative methods to synthesize and analyze the available literature on a particular topic. It aims to provide a more comprehensive understanding of the research question by combining different types of evidence.

Parts of Literature Review

Parts of a literature review are as follows:

Introduction

The introduction of a literature review typically provides background information on the research topic and why it is important. It outlines the objectives of the review, the research question or hypothesis, and the scope of the review.

Literature Search

This section outlines the search strategy and databases used to identify relevant literature. The search terms used, inclusion and exclusion criteria, and any limitations of the search are described.

Literature Analysis

The literature analysis is the main body of the literature review. This section summarizes and synthesizes the literature that is relevant to the research question or hypothesis. The review should be organized thematically, chronologically, or by methodology, depending on the research objectives.

Critical Evaluation

Critical evaluation involves assessing the quality and validity of the literature. This includes evaluating the reliability and validity of the studies reviewed, the methodology used, and the strength of the evidence.

The conclusion of the literature review should summarize the main findings, identify any gaps in the literature, and suggest areas for future research. It should also reiterate the importance of the research question or hypothesis and the contribution of the literature review to the overall research project.

The references list includes all the sources cited in the literature review, and follows a specific referencing style (e.g., APA, MLA, Harvard).

How to write Literature Review

Here are some steps to follow when writing a literature review:

  • Define your research question or topic : Before starting your literature review, it is essential to define your research question or topic. This will help you identify relevant literature and determine the scope of your review.
  • Conduct a comprehensive search: Use databases and search engines to find relevant literature. Look for peer-reviewed articles, books, and other academic sources that are relevant to your research question or topic.
  • Evaluate the sources: Once you have found potential sources, evaluate them critically to determine their relevance, credibility, and quality. Look for recent publications, reputable authors, and reliable sources of data and evidence.
  • Organize your sources: Group the sources by theme, method, or research question. This will help you identify similarities and differences among the literature, and provide a structure for your literature review.
  • Analyze and synthesize the literature : Analyze each source in depth, identifying the key findings, methodologies, and conclusions. Then, synthesize the information from the sources, identifying patterns and themes in the literature.
  • Write the literature review : Start with an introduction that provides an overview of the topic and the purpose of the literature review. Then, organize the literature according to your chosen structure, and analyze and synthesize the sources. Finally, provide a conclusion that summarizes the key findings of the literature review, identifies gaps in knowledge, and suggests areas for future research.
  • Edit and proofread: Once you have written your literature review, edit and proofread it carefully to ensure that it is well-organized, clear, and concise.

Examples of Literature Review

Here’s an example of how a literature review can be conducted for a thesis on the topic of “ The Impact of Social Media on Teenagers’ Mental Health”:

  • Start by identifying the key terms related to your research topic. In this case, the key terms are “social media,” “teenagers,” and “mental health.”
  • Use academic databases like Google Scholar, JSTOR, or PubMed to search for relevant articles, books, and other publications. Use these keywords in your search to narrow down your results.
  • Evaluate the sources you find to determine if they are relevant to your research question. You may want to consider the publication date, author’s credentials, and the journal or book publisher.
  • Begin reading and taking notes on each source, paying attention to key findings, methodologies used, and any gaps in the research.
  • Organize your findings into themes or categories. For example, you might categorize your sources into those that examine the impact of social media on self-esteem, those that explore the effects of cyberbullying, and those that investigate the relationship between social media use and depression.
  • Synthesize your findings by summarizing the key themes and highlighting any gaps or inconsistencies in the research. Identify areas where further research is needed.
  • Use your literature review to inform your research questions and hypotheses for your thesis.

For example, after conducting a literature review on the impact of social media on teenagers’ mental health, a thesis might look like this:

“Using a mixed-methods approach, this study aims to investigate the relationship between social media use and mental health outcomes in teenagers. Specifically, the study will examine the effects of cyberbullying, social comparison, and excessive social media use on self-esteem, anxiety, and depression. Through an analysis of survey data and qualitative interviews with teenagers, the study will provide insight into the complex relationship between social media use and mental health outcomes, and identify strategies for promoting positive mental health outcomes in young people.”

Reference: Smith, J., Jones, M., & Lee, S. (2019). The effects of social media use on adolescent mental health: A systematic review. Journal of Adolescent Health, 65(2), 154-165. doi:10.1016/j.jadohealth.2019.03.024

Reference Example: Author, A. A., Author, B. B., & Author, C. C. (Year). Title of article. Title of Journal, volume number(issue number), page range. doi:0000000/000000000000 or URL

Applications of Literature Review

some applications of literature review in different fields:

  • Social Sciences: In social sciences, literature reviews are used to identify gaps in existing research, to develop research questions, and to provide a theoretical framework for research. Literature reviews are commonly used in fields such as sociology, psychology, anthropology, and political science.
  • Natural Sciences: In natural sciences, literature reviews are used to summarize and evaluate the current state of knowledge in a particular field or subfield. Literature reviews can help researchers identify areas where more research is needed and provide insights into the latest developments in a particular field. Fields such as biology, chemistry, and physics commonly use literature reviews.
  • Health Sciences: In health sciences, literature reviews are used to evaluate the effectiveness of treatments, identify best practices, and determine areas where more research is needed. Literature reviews are commonly used in fields such as medicine, nursing, and public health.
  • Humanities: In humanities, literature reviews are used to identify gaps in existing knowledge, develop new interpretations of texts or cultural artifacts, and provide a theoretical framework for research. Literature reviews are commonly used in fields such as history, literary studies, and philosophy.

Role of Literature Review in Research

Here are some applications of literature review in research:

  • Identifying Research Gaps : Literature review helps researchers identify gaps in existing research and literature related to their research question. This allows them to develop new research questions and hypotheses to fill those gaps.
  • Developing Theoretical Framework: Literature review helps researchers develop a theoretical framework for their research. By analyzing and synthesizing existing literature, researchers can identify the key concepts, theories, and models that are relevant to their research.
  • Selecting Research Methods : Literature review helps researchers select appropriate research methods and techniques based on previous research. It also helps researchers to identify potential biases or limitations of certain methods and techniques.
  • Data Collection and Analysis: Literature review helps researchers in data collection and analysis by providing a foundation for the development of data collection instruments and methods. It also helps researchers to identify relevant data sources and identify potential data analysis techniques.
  • Communicating Results: Literature review helps researchers to communicate their results effectively by providing a context for their research. It also helps to justify the significance of their findings in relation to existing research and literature.

Purpose of Literature Review

Some of the specific purposes of a literature review are as follows:

  • To provide context: A literature review helps to provide context for your research by situating it within the broader body of literature on the topic.
  • To identify gaps and inconsistencies: A literature review helps to identify areas where further research is needed or where there are inconsistencies in the existing literature.
  • To synthesize information: A literature review helps to synthesize the information from multiple sources and present a coherent and comprehensive picture of the current state of knowledge on the topic.
  • To identify key concepts and theories : A literature review helps to identify key concepts and theories that are relevant to your research question and provide a theoretical framework for your study.
  • To inform research design: A literature review can inform the design of your research study by identifying appropriate research methods, data sources, and research questions.

Characteristics of Literature Review

Some Characteristics of Literature Review are as follows:

  • Identifying gaps in knowledge: A literature review helps to identify gaps in the existing knowledge and research on a specific topic or research question. By analyzing and synthesizing the literature, you can identify areas where further research is needed and where new insights can be gained.
  • Establishing the significance of your research: A literature review helps to establish the significance of your own research by placing it in the context of existing research. By demonstrating the relevance of your research to the existing literature, you can establish its importance and value.
  • Informing research design and methodology : A literature review helps to inform research design and methodology by identifying the most appropriate research methods, techniques, and instruments. By reviewing the literature, you can identify the strengths and limitations of different research methods and techniques, and select the most appropriate ones for your own research.
  • Supporting arguments and claims: A literature review provides evidence to support arguments and claims made in academic writing. By citing and analyzing the literature, you can provide a solid foundation for your own arguments and claims.
  • I dentifying potential collaborators and mentors: A literature review can help identify potential collaborators and mentors by identifying researchers and practitioners who are working on related topics or using similar methods. By building relationships with these individuals, you can gain valuable insights and support for your own research and practice.
  • Keeping up-to-date with the latest research : A literature review helps to keep you up-to-date with the latest research on a specific topic or research question. By regularly reviewing the literature, you can stay informed about the latest findings and developments in your field.

Advantages of Literature Review

There are several advantages to conducting a literature review as part of a research project, including:

  • Establishing the significance of the research : A literature review helps to establish the significance of the research by demonstrating the gap or problem in the existing literature that the study aims to address.
  • Identifying key concepts and theories: A literature review can help to identify key concepts and theories that are relevant to the research question, and provide a theoretical framework for the study.
  • Supporting the research methodology : A literature review can inform the research methodology by identifying appropriate research methods, data sources, and research questions.
  • Providing a comprehensive overview of the literature : A literature review provides a comprehensive overview of the current state of knowledge on a topic, allowing the researcher to identify key themes, debates, and areas of agreement or disagreement.
  • Identifying potential research questions: A literature review can help to identify potential research questions and areas for further investigation.
  • Avoiding duplication of research: A literature review can help to avoid duplication of research by identifying what has already been done on a topic, and what remains to be done.
  • Enhancing the credibility of the research : A literature review helps to enhance the credibility of the research by demonstrating the researcher’s knowledge of the existing literature and their ability to situate their research within a broader context.

Limitations of Literature Review

Limitations of Literature Review are as follows:

  • Limited scope : Literature reviews can only cover the existing literature on a particular topic, which may be limited in scope or depth.
  • Publication bias : Literature reviews may be influenced by publication bias, which occurs when researchers are more likely to publish positive results than negative ones. This can lead to an incomplete or biased picture of the literature.
  • Quality of sources : The quality of the literature reviewed can vary widely, and not all sources may be reliable or valid.
  • Time-limited: Literature reviews can become quickly outdated as new research is published, making it difficult to keep up with the latest developments in a field.
  • Subjective interpretation : Literature reviews can be subjective, and the interpretation of the findings can vary depending on the researcher’s perspective or bias.
  • Lack of original data : Literature reviews do not generate new data, but rather rely on the analysis of existing studies.
  • Risk of plagiarism: It is important to ensure that literature reviews do not inadvertently contain plagiarism, which can occur when researchers use the work of others without proper attribution.

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A literature review surveys scholarly articles, books and other sources relevant to a particular issue, area of research, or theory, and by so doing, providing a description, summary, and critical evaluation of these works. Literature reviews are designed to provide an overview of sources you have explored while researching a particular topic and to demonstrate to your readers how your research fits into the larger field of study.

All contect is from a Literature Review please refer to the sub-tab under The Literature Review created by Dr. Robert Larabee.

Importance of a Good Literature Review

A literature review may consist of simple a summary of key sources, but it usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

  • give a new interpretation of old material or combine new with old interpretations,
  • trace the intellectual progression of the field, including major debates,
  • depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant, or
  • usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

The purpose of a literature review is to:

  • Place each work in the context of its contribution to the understanding of the research problem being studied,
  • Describe the relationship of each work to the others under consideration,
  • Identify new ways to interpret, and shed light on any gaps in previous research,
  • Resolve conflicts amongst seemingly contradictory previous studies,
  • Identify areas of prior scholarship to prevent duplication of effort,
  • Point the way in fulfilling a need for additional research, and
  • Locate your own research within the context of existing literature.

All contect is from The Literature Review created by Dr. Robert Larabee.

Types of Literature Reviews

As Kennedy (2007) notes*, it is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the original studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally that become part of the lore of field. In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews.

Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are several approaches to how they can be done, depending upon the type of analysis underpinning your study. Listed below are definitions of types of literature reviews:

Argumentative Review      This form examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to to make summary claims of the sort found in systematic reviews.

Integrative Review      Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication.

Historical Review      Few things rest in isolation from historical precedent. Historical reviews are focused on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review      A review does not always focus on what someone said [content], but how they said it [method of analysis]. This approach provides a framework of understanding at different levels (i.e. those of theory, substantive fields, research approaches and data collection and analysis techniques), enables researchers to draw on a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection and data analysis, and helps highlight many ethical issues which we should be aware of and consider as we go through our study.

Systematic Review      This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyse data from the studies that are included in the review. Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?"

Theoretical Review      The purpose of this form is to concretely examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review help establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

* Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following :

  • An overview of the subject, issue or theory under consideration, along with the objectives of the literature review,
  • Division of works under review into themes or categories (e.g. works that support of a particular position, those against, and those offering alternative approaches entirely),
  • An explanation of how each work is similar to and how it varies from the others,
  • Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research

The critical evaluation of each work should consider :

  • Provenance -- what are the author's credentials? Are the author's arguments supported by evidence (e.g. primary historical material, case studies, narratives, statistics, recent scientific findings)?
  • Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
  • Persuasiveness -- which of the author's theses are most/least convincing?
  • Value -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  The Development of the Literature Review

Four stages : 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not very specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources should I include? 2.  What types of sources should I review (books, journal articles, websites)? 3.  Should I summarize, synthesize, or critique your sources by discussing a common theme or issue? 4.  Should I evaluate the sources? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature reviews. Read them to get a sense of the types of themes you might want to look for in your own research or ways to organize your final review. The bibliography or reference section of sources you've already read are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make your job easier if you first limit scope of the research problem. A good strategy is to begin by searching the HOMER catalog for books about the topic and review their contents for chapters that focus on more specific issues. You can also review the subject indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is very common in the sciences where research conducted only two years ago could be obsolete. However, when writing a review in the social sciences, a survey of the history of the literature may be what is needed because what is important is how perspectives have changed over the years or within a certain time period. Try sorting through some other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to consider what is consider by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronological of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression of revealed a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic (“conceptual categories”) Thematic reviews of literature are organized around a topic or issue, rather than the progression of time. However, progression of time may still be an important factor in a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it will still be organized chronologically reflecting technological developments in media. The only difference here between a "chronological" and a "thematic" approach is what is emphasized the most: the role of the Internet in presidential politics. Note however that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Interbnet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you but include only what is necessary for the reader to locate your study within the larger scholarship framework.

Here are examples of other sections you may need to include depending on the type of review you write:

  • Current Situation : information necessary to understand the topic or focus of the literature review.
  • History : the chronological progression of the field, the literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
  • Selection Methods : the criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed articles and journals.
  • Standards : the way in which you present your information.
  • Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review in this sense is just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence to show that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Use Quotes Sparingly Some short quotes are okay if you want to emphasize a point, or if what the author said just cannot be rewritten in your own words. Sometimes you may need to quote certain terms that were coined by the author, not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute your own summary and interpretation of the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to their own work. Keep Your Own Voice While the literature review presents others' ideas, your voice (the writer's) should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

The most common mistakes made in reviewing social science research literature are that the researcher:

  • does not clearly relate the findings of the literature review to the research problem;
  • does not take sufficient time to define and identify the most relevent sources to use in the literature review related to the research problem;
  • relies exclusively on secondary analytical sources rather than including primary research studies or data;
  • uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
  • does not describe the search procedures that were used in the literature review;
  • reports isolated statistical results rather than sythesizing them in chi-squared or meta-analytic methods; and,
  • only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions. Consult with a librarian about identifying research databases in other disciplines; almost every discipline has at least one comprehensive database devoted to indexing its research literature.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to this part of writing a research paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. How are they structuring their ideas? What methods have they used to study the problem? What sources have they cited to support of their conclusions? How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've adequately reviewed the research literature:

  • Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a dead end. At this point consider: Does your study extend current research?  Does it forge as new path? Or, does is merely add more of the same thing being said?
  • Look at the sources authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been introduced to the research question.
  • Search the World of Knowledge Citation database and Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline.
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17 strong academic phrases to write your literature review (+ real examples)

literature review on previous studies

A well-written academic literature review not only builds upon existing knowledge and publications but also involves critical reflection, comparison, contrast, and identifying research gaps. The following 17 strong academic key phrases can assist you in writing a critical and reflective literature review.

Academic key phrases to present existing knowledge in a literature review

The topic has received significant interest within the wider literature..

Example: “ The topic of big data and its integration with AI has received significant interest within the wider literature .” ( Dwivedi et al. 2021, p. 4 )

The topic gained considerable attention in the academic literature in…

Studies have identified….

Example: “ Studies have identified the complexities of implementing AI based systems within government and the public sector .” ( Dwivedi et al. 2021, p. 6 )

Researchers have discussed…

Recent work demonstrated that….

Example: “Recent work demonstrated that dune grasses with similar morphological traits can build contrasting landscapes due to differences in their spatial shoot organization.” ( Van de Ven, 2022 et al., p. 1339 )

Existing research frequently attributes…

Prior research has hypothesized that…, prior studies have found that….

Example:  “ Prior studies have found that court-referred individuals are more likely to complete relationship violence intervention programs (RVIP) than self-referred individuals. ” ( Evans et al. 2022, p. 1 )

Academic key phrases to contrast and compare findings in a literature review

While some scholars…, others…, the findings of scholar a showcase that… . scholar b , on the other hand, found….

Example: “ The findings of Arinto (2016) call for administrators concerning the design of faculty development programs, provision of faculty support, and strategic planning for online distance learning implementation across the institution. Francisco and Nuqui (2020) on the other hand found that the new normal leadership is an adaptive one while staying strong on their commitment. ” ( Asio and Bayucca, 2021, p. 20 )

Interestingly, all the arguments refer to…

This argument is similar to….

If you are looking to elevate your writing and editing skills, I highly recommend enrolling in the course “ Good with Words: Writing and Editing Specialization “, which is a 4 course series offered by the University of Michigan. This comprehensive program is conveniently available as an online course on Coursera, allowing you to learn at your own pace. Plus, upon successful completion, you’ll have the opportunity to earn a valuable certificate to showcase your newfound expertise!

Academic key phrases to highlight research gaps in a literature review

Yet, it remains unknown how…, there is, however, still little research on…, existing studies have failed to address….

Example: “ University–industry relations (UIR) are usually analysed by the knowledge transfer channels, but existing studies have failed to address what knowledge content is being transferred – impacting the technology output aimed by the partnership.”  (Dalmarco et al. 2019, p. 1314 )

Several scholars have recommended to move away…

New approaches are needed to address…, master academia, get new content delivered directly to your inbox, 26 powerful academic phrases to write your introduction (+ real examples), 13 awesome academic phrases to write your methodology (+ real examples), related articles, how to paraphrase a quote: 4 simple strategies, the different stages in the manuscript publication process, energy management in academia, how to disagree with reviewers (with examples).

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Writing the Literature Review

Barry Mauer and John Venecek

Note: Not all research papers contain literature reviews in their finished or published form. Check your assignment and guidelines to see if one is required. Even if a literature review is not required, you still need to read the available scholarly literature on your topic so you can join the scholarly conversation.

  • The Literature Review

What is the Purpose of the Review?

What is the scope of the review, strategies for getting started, types of literature reviews, composition guidelines, how to locate reviews by discipline, key takeaways.

We also provide the following activities:

Types of Literature Reviews [Refresher]

Writing the literature review [refresher], the literature review [1].

Conducting a literary studies research project involves time and effort, with much of it going towards the development of a literature review . A literature review might fill several pages of your research paper and usually appears soon after an introduction but before you present your detailed argument. A literature review provides your audience with an overview of the available research about your area(s) of study, including the literary work, your theory, and methodology. The literature review demonstrates how these scholarly discussions have changed over time, and it allows you to position your research in relation to research that has come before yours. Your aim is to present the discussion up to this point. Depending on the nature of the assignment, you may also include your critical commentary on prior research, noting among this material the weaker and stronger arguments, breakthroughs and dead ends, blind spots and opportunities, the invention of key terms and methods, mistakes as well as misreadings, and so on.

Once you have gathered the research materials you need for your literature review, you have another task: conducting an analysis on the research to see where your original contribution fits into the scholarly conversation. As the saying goes, “we are standing on the shoulders of giants.” Your job is to show a portrait of these giants to your audience, and to show how your work relates to the portrait. On many scholarly topics, literature reviews already exist. You may refer to such existing reviews within your own, indicating any materials might have been overlooked, new developments that have arisen since the publication of the existing literature review, and new perspectives or insights you have about the materials.

Some beginning researchers try to tear down the work of other researchers in an effort to make their own work look good by comparison. It rarely works. First, it tends to make your audience skeptical of your claims. Second, it ignores the fact that even the mistakes, blind spots, and failures of other researchers contribute something to our knowledge. Albert Einstein didn’t disrespect Sir Isaac Newton by saying Newton’s theory of space was wrong and terrible and that Einstein’s own theory was great by comparison. He built upon Newton’s work, showing how it could be improved. If, however, a researcher willfully set out to deceive or distort or to tear down the work of other scholars without good reason, then their work does not deserve such deference.

Most literature reviews appear after the introduction. It presents your reader with relevant information about the scholarly discussion up to now. Later in your paper, you discuss your contribution. Before you begin work on your literature review, let’s discuss what we mean by “literature”; understand the purpose and scope of the review; establish criteria for selecting, organizing, and interpreting your findings; and discuss how to connect your findings to your research question.

Many students seek to “find sources that agree with my claim or idea.” That approach is too narrow, in our view. If we use such an approach, we may get the following results:

  • Because we can find sources that agree with almost any claim, readers will wonder whether your claims are weak and the sources are cherry picked.
  • While literary scholars sometimes cite authorities to support their claims, they don’t rely only on authority. They respect authority, but not too much. Your own claims need to rely more on evidence (from the literary text, historical and biographical information), and your critical and creative reasoning skills.
  • Scholarship is a conversation; thus, the goal is less about finding agreement and more about joining the conversation with the aim of making a valuable contribution to the discussion.

The literature review provides your reader with an overview of the existing research about your topic or problem. It provides the context necessary for your reader to catch up with the scholarly conversation and then to appreciate the value of your contribution to it. The literature review sharpens the focus of your research and demonstrates your knowledge and understanding of the scholarly conversation around your topic, which, in turn, helps establish your credibility as a researcher.

Creating the literature review involves more than gathering citations. It is a qualitative process through which you will discover what is already known about your topic, and identify the key authorities, methods, and theoretical foundations, so you can begin to position your contributions within the scholarly conversation.

Defining the scope of your review will also help you establish criteria to determine the relevance of the sources you are finding. At this stage, you are not reading in-depth; instead, you are skimming through what has already been published and identifying the major concepts, theories, methodologies, and methods present within these published works. You should also be identifying connections, tensions, and contradictions within the already published works of your topic or problem. This involves building on the knowledge of others and understanding what methods, measures, and models we have inherited from previous researchers in our field.

Literature Reviews: Common Errors Made When Conducting a Literature Review [12 min 22 sec]

Video provided courtesy of the Center for Quality Research (CQR)

A literature review helps your reader understand the relationship of your research project to the work of other scholars. It covers the existing knowledge about a problem, and allows you to show the relevance/significance of your contribution to the discussion. Your reader may or may not have read scholarly literature about the theories, methodologies, and literary works you are discussing. But they want to know that you have read it and have thought about it. Your literature review provides not only a summary of the existing scholarship for readers; it also offers your perspective on it.

Begin your work on the literature review by synthesizing the various sources in your annotated bibliography .

For advice on Synthesizing Sources, consider the following from The Purdue Online Writing Lab: [2]

Note that  synthesizing is not the same as summarizing .

  • A summary restates the information in one or more sources without providing new insight or reaching new conclusions.
  • A synthesis draws on multiple sources to reach a broader conclusion.
  • Don’t force a relationship between sources if there isn’t one. Not all of your sources have to complement one another.
  • Do your best to highlight the relationships between sources in very clear ways.
  • Don’t ignore any outliers in your research. It’s important to take note of every perspective (even those that disagree with your broader conclusions).

Not all humanities research projects contain literature reviews, but many do. Keep in mind that the type of literature review you choose (see list below) pertains to the secondary research – other scholarly sources – and not to the primary literary work. For instance, a literature review about Kate Chopin’s writing will be your thoughts about the scholarship on Chopin and not about Chopin’s text itself. You are summarizing what you see in the scholarly literature about Chopin’s writing. The literature review puts you in the position of authority not just on Chopin’s writing but on the scholarship about her writing. You are seeking to understand what scholars have said about her work. Scholars might belong to different schools of thought (psychoanalytic, feminist, Marxist, etc.). They might make different arguments about Chopin. They might use different methodological approaches. 

If your research involves two or more theories, such as psychology and genre studies, you may need to create multiple literature reviews, one for each theory or methodology. If the theories overlap with each other significantly (i.e., Marxism and Cultural Studies), you may combine them. Your literature review need not include everything about the subject area – you would need to write a book to cover a single theory – but only those concepts and methods that are most relevant to your research problem.

Factors to Consider When Developing Your Literature Review

  • Determine the Scope : How broad or narrow should your literature review be? You may want to focus on recent scholarship only, or on a particular school of thought in the literature. Your scope is determined by your purpose; what is it you aim to achieve with your research?
  • Establish Criteria : We discussed the importance of defining the purpose and scope of your review on the previous page, but it’s worth reviewing here as well. This step will help you establish important criteria and focus your searching. For example, how many sources will you need? What types of sources (primary, secondary, statistics, media)? Is currency important? Do you know who the prominent authors or theorists are in your subject area? Take some time to map out these or other important factors before you begin searching journals and databases.
  • Consider Your Audience : Unlike a work cited page or an annotated bibliography, both of which are lists of sources, a literature review is essayistic and can be considered a precursor to your final paper. Therefore, it should be written in your own voice, and it should be geared toward a specific audience. Considering audience during this early stage will help focus your final paper as well.
  • Find Models : We’ll discuss the different types of literature reviews and how to locate examples in the section below. However, even if you’re undecided about what type of review will work best for you, you may want to review some example literature reviews to get a sense of what they look like before you begin your own.

One piece of advice before starting: look for existing literature reviews on your area of scholarship. You can build on the work that other scholars have put into reviewing the scholarly literature. There’s no need to completely “reinvent the wheel” if some of the work is already done.

Scholars sometimes publish “stand-alone” literature reviews that are not part of a larger work; such literature reviews are valuable contributions to the field, as they summarize the state of knowledge for other scholars.

Maria J. Grant and Andrew Booth’s “A Typology of Reviews” identifies 14 distinct types of literature reviews. Further, the UCLA library created a chart to complement the article and for easy comparison of those 14 types of reviews. This section provides a brief summary of the most common literature reviews. For a more complete analysis, please see the full article and the chart .

To choose the most appropriate structure, put yourself in your reader’s shoes and think through their need for information. The literature review is about providing context for your contribution. How much context do people need? Keep it to the minimum necessary; compressing a lot of information into a small amount of text is a must.

These structures are not meant to be straightjackets but tools to help you organize your research. If you find that the tool is working, then keep using it. If not, switch tools or modify the one you are using. Keep in mind that the types of literature reviews are just different ways of organizing information. So, you can discuss literary trends without organizing your review of secondary literature by trend; your discussion can be organized by theory or theme, for examples. In our literature reviews, we are not recounting other scholars’ arguments at length but merely providing key concepts so we can summarize the discussion so far and position our own claims. You don’t have to adhere strictly to one structure or another. They are just organizing tools that help you manage your material (and help your reader make sense of it).

Types of Reviews

  • Traditional or narrative reviews : This approach will generate a comprehensive, critical analysis of the published research on your topic. However, rather than merely compiling as many sources as possible, use this approach to establish a theoretical framework for your paper, establish trends, and identify gaps in the research. This process should bring your research question into clearer focus and help define a thesis that you will argue for in your paper. This is perhaps the most common and general type of literature review. The examples listed below are all designed to serve a more specific purpose.
  • Argumentative : The purpose of an argumentative literature review is to select sources for the purpose of supporting or refuting a specific claim. While this type of review can help the author make a strong case for or against an issue, they can also be prone to claims of bias. Later in this textbook, we will read about the distinction between warranted and unwarranted bias . One is ok and the other is not.
  • Chronological : A chronological review is used when the author wants to demonstrate the progression of how a theory, methodology, or issue has progressed over time. This method is most effective when there is a clear chronological path to the research about a specific historical event or trend as opposed to a more recursive theoretical concept.
  • By trend : This is similar to the chronological approach except it focuses on clearly-defined trends rather than date ranges. This would be most appropriate if you want to illustrate changing perspectives or attitudes about a given issue when specific date ranges are less important than the ebb and flow of the trend.
  • Thematic : In this type of literature review, the author will select specific themes that he or she feels are important to understanding a larger topic or concept. Then, the author will organize the sources around those themes, which are often based on relevance or importance. The value of this method is that the process of organizing the review by theme is similar to constructing an argument. This can help the author see how resources connect to each other and determine how as well as why specific sources support their thesis.
  • Theoretical : The goal of this type of review is to examine how theory has shaped the research on a given topic. It establishes existing theoretical models, their connections, and how extensively they have been developed in the published research. For example, Jada applied critical race theory to her analysis of Sonny’s Blues , but she might also consider conducting a more comprehensive review of other theoretical frameworks such as feminism, Marxism, or postmodernism. Doing so could provide insight into alternate readings, and help her identify theoretical gaps such as unexplored or under-developed approaches to Baldwin’s work.
  • Methodological : The approach focuses on the various methodologies used by researchers in a specific area rather than an analysis of their findings. In this case, you would create a framework of approaches to data collection related to your topic or research question. This is perhaps more common in education or the social and hard sciences where published research often includes a methods section, but it is sometimes appropriate for the digital humanities as well.
  • Scoping : The aim of a scoping review is to provide a comprehensive overview or map of the published research or evidence related to a research question. This might be considered a prelude to a systematic review that would take the scoping review one step further toward answering a clearly defined research question. See below for more details.
  • Systematic : The systematic review is most appropriate when you have a clearly-defined research question and have established criteria for the types of sources you need. In this way, the systematic review is less exploratory than other types of reviews. Rather, it is comprehensive, strategic, and focused on answering a specific research question. For this reason, the systematic review is more common in the health and social sciences, where comprehensiveness is more important. Literature reviews in the Humanities are not usually exhaustive but tend to show only the most representative or salient developments in the scholarship.
  • Meta-analysis : Does your research deal with statistics or large amounts of data? If so, then a meta-analysis might be best for you rather than providing a critical review, the meta-analysis will summarize and synthesize the results of numerous studies that involve statistics or data to provide a more comprehensive picture than would be possible from just one study.

An argumentative literature review presents and takes sides in scholarly arguments about the literary work. It makes arguments about other scholars’ work. It does not necessarily involve a claim that the literary work is itself making an argument. Likewise, a chronological literature review presents the scholarly literature in chronological order.

You don’t need to keep strictly to one type. Scholars often combine features from various types of literature reviews. A sample review that combines the follow types –

  • Argumentative
  • Theoretical
  • Methodological

– is the excellent work of Eiranen, Reetta, Mari Hatavara, Ville Kivimäki, Maria Mäkelä & Raisa Maria Toivo (2022) “ Narrative and Experience: Interdisciplinary Methodologies between History and Narratology , ” Scandinavian Journal of History , 47:1, 1-15

When writing your literature review, please follow these pointers:

  • Conduct systematic searches
  • Use Evidence
  • Be Selective
  • Use Quotes Sparingly
  • Summarize & Synthesize
  • Use Caution when Paraphrasing
  • Use Your Own Voice

Advice from James Mason University’s “Literature Reviews: An Overview”

literature review on previous studies

A note on synthesizing : Don’t make the common mistake of summarizing individual studies or articles one after the other. The goal is to synthesize — that is, to make observations about groups of studies. Synthesis often uses language like this:

  • Much of the literature on [topic x ] focuses on [major themes].
  • In recent years, researchers have begun investigating [facets a , b , and c ] of [topic x ].
  • The studies in this review of [topic x ] confirm / suggest / call into question / support [idea / practice / finding / method / theory / guideline y ].
  • In the reviewed studies [variable x ] was generally associated with higher / lower rates of [outcome y ].
  • A limitation of some / most / all of these studies is [ y ].

Please see this sample annotated literature review  from James Mason University.

Structure of a literature review [2]

  • Problematization: The 2 to 3 pages of problematization are a distinct, iterative, step. It may take doing such a statement a few times before moving forward to writing the actual paper.
  • Search: Write down your keyword sets, your updated keyword sets, and databases. It is perfectly within a reviewer’s rights to ask for these details.
  • Summary: Really getting to know major themes requires some annotation of articles. You want to identify core papers and themes and write about them. This helps you really learn the material. [ChatGPT or Wikipedia are no substitute for deep engagement with a paper.]
  • Argument: Either outline or create a slide deck that help you express the arguments in your paper. Read them out loud. Have friends look at them. Present them. [Every literature review has an argument. If not, it’s a summary. A summary does not merit publication in a top outlet.]
  • Unpacking: Once you’ve nailed the short pitch, unpack the full argument. [ a) Take time in each major section to map out a) the argument, b) the supporting evidence, and the takeaway. b) Take those major sections, reconcile them, make sure they don’t overlap, then move on to writing. c) Sketch out the paper’s sections, tables, figures, and appendices.]
  • Writing: Writing is the easy part. You can always put words to the screen. [Revising and improving is hard. Make time to write every day. Improving requires feedback. Find a writing partner to give feedback. Create your tables and figures. Write to them. Make sure the words in the paper align to the visuals.]
  • Communicate: When the paper is done, go back and create a paper presentation. [I do this for the papers that I’m most serious about. The act of storyboarding helps me sort out the small pieces of the story that don’t fit together. If I really want it to succeed, I present it. The act of presenting helps me get it right. My best papers sometimes take seven or eight presentations to get it right. Then I return to the paper and fine tune it. Only then, does it have a shot at a top outlet.]

Literature reviews can be published as part of a scholarly article, often after the introduction and sometimes with a header, but they can also be published as a standalone essay. To find examples of what reviews look like in your discipline, choose an appropriate subject database (such as MLA for literary criticism) and conduct a keyword search with the term “Literature Review” added in quotes:

Lit review_1.PNG

Not only do these examples demonstrate how to structure different types of literature reviews, but some offer insights into trends and directions for future research. In the next section, we’ll take a closer look at some reading strategies to help guide you through this process.

Since scholars already have produced literature reviews on various scholarly conversations, you don’t always need to “reinvent the wheel” (start a literature review from nothing). You can find a published literature review and update it or amend it; scholars do that all the time. However, you must properly cite work you incorporate from others.

image

Provide your audience with an overview of the available research on your area(s) of study, including: the literary work, theory, methodology, and method (if the assignment permits). Skip the literature review.
Review only materials about the literary work but not about theory, methodology, and method.
Provide your critical commentary on the materials (if the assignment permits). Present previous research as though it is all equally good or useful.
Build on the research found in other scholarship. Aim to tear down the research of other scholars.
  • What types of literature review will you be using for your paper? Why did you make this selection over others? If you haven’t made a selection yet, which types are you considering?
  • What specific challenges do you face in following a literature review structure?
  • If there are any elements of your assignment that need clarification, please list them.
  • What was the most important lesson you learned from this page? What point was confusing or difficult to understand?
  • In the “Back Matter” of this book, you will find a page titled “Rubrics.” On that page, we provide a rubric for Creating a Literature Review ↵
  • Richard West, Brigham Young University, amended by Jason Thatcher, Temple University - https://www.linkedin.com/posts/jason-thatcher-0329764_academicwriting-topten2023-activity-7146507675021766656-BB0O ↵

Writing the Literature Review Copyright © 2021 by Barry Mauer and John Venecek is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Doing Diligence

The first step in any systematic review or other type of evidence synthesis project is to search the existing literature to identify what research, both primary and secondary, has already been conducted. As with any publication, your review will likely need to be original/novel in order to be of interest to editors and publications. In addition, duplicating a previously done study may not add new understandings to the body of evidence. Here are some questions for consideration:

  • Has your research question already been answered?
  • How recently has the existing secondary research been conducted/published?
  • Does the existing secondary research need to be updated due to new original research that has been conducted after its publication?
  • Is there existing secondary research that answers a different research question than the one you want to answer?
  • How does your question, methodology, or timing differ from existing research?

All of these questions will help you identify  why  you would conduct this new study. It is disheartening (at best) to learn part way through an evidence synthesis project that the research has already been conducted.

Search Published Literature

Search for published studies that address your research question. This should be done in several different databases to ensure you have a solid sense of what has already been accomplished. It will also inform the way that you create your search strategy for this study, as you'll learn the types of words that are used to describe this research question, publications that have published these types of studies, and how the articles have been indexed within the databases. Below are a few databases that you might consider searching for health sciences publications.

  • PubMed This link to PubMed is for those affiliated with WSU. PubMed comprises more than 30 million citations for biomedical literature from MEDLINE, life science journals and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.
  • EMBASE Embase is an abstract and Indexing (A & I) database covering over 8,500 journal titles, 30 million articles back to 1974, all disciplines of medicine and biomedical science, and includes substantial coverage of Allied Health subjects.
  • CINAHL Complete (EBSCOHost) CINAHL Complete is the world's most comprehensive source of full-text for nursing & allied health journals, providing full text for more than 1,300 journals indexed in CINAHL.
  • APA PsycInfo (ProQuest) This link opens in a new window An index with summaries of citations to articles in over 1,300 psychology research journals. Articles date from 1806 - present. Note: There are less than 146 records with publication dates prior to 1890. Updated weekly.

Search for Preregistrations

In addition to finding articles that have already been published, you will need to search registries to see if others are currently in the process of researching this topic/question, just as you would for clinical research. Here are a few repositories for you to search:

  • Open Science Framework (OSF) Registries
  • Cochrane Preregistrations
  • Campbell Preregistrations

Identification of Review Type

While considering conducting a literature review, you should compare your draft research question to the different review types that can be used to explore the existing research. Some types, such as narrative reviews, do not consider the literature search as a formal methodology, while others such as Systematic Reviews view the literature search as a reproducible research methodology.

As a first step, search the literature for other published articles and studies that address the same or similar research question. The quantity, quality, and depth of existing research will be an important component in deciding on a review type.

Selection of the review type includes not only aspirations for what the review could accomplish, but also pragmatic limitations based on how much time the team has to devote to the project, how many team members are participating in the review, and deadlines for the review completion (such as the date of an upcoming conference). In addition, the breadth of the research question may result in a large number of search results; this should be considered in terms of the number of team members involved in the screening and abstraction of the included studies, as well as whether the research question should be narrowed or include more limitations/exclusion criteria in order to satisfy the practical limitations of the team.

Use the decision tree below from Cornell University to determine what type of review best suits your question/topic and available resources. The PDF is linked for you to view/download along with descriptions of the review types, with an image of the decision tree displayed on this page. To learn more about the different types, purposes, and methods of reviews, click the "Types of Reviews" link below the decision tree. 

Types of Reviews

  • What Type of Review is Right For You? | Decision Tree

literature review on previous studies

Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91–108. doi: 10.1111/j.1471-1842.2009.00848.x 

Label Description Search Appraisal Synthesis Analysis
Critical Review Aims to demonstrate writer has extensively researched literature and critically evaluated its quality. Goes beyond mere description to include degree of analysis and conceptual innovation. Typically results in hypothesis or model Seeks to identify most significant items in the field No formal quality assessment. Attempts to evaluate according to contribution Typically narrative, perhaps conceptual or chronological Significant component: seeks to identify conceptual contribution to embody existing or derive new theory
Literature Review Generic term: published materials that provide examination of recent or current literature. Can cover wide range of subjects at various levels of completeness and comprehensiveness. May include research findings May or may not include comprehensive searching May or may not include quality assessment Typically narrative Analysis may be chronological, conceptual, thematic, etc.
Mapping Review / Systematic Map Map out and categorize existing literature from which to commission further reviews and/or primary research by identifying gaps in research literature Completeness of searching determined by time/scope constraints No formal quality assessment May be graphical and tabular Characterizes quantity and quality of literature, perhaps by study design and other key features. May identify need for primary or secondary research
Meta-Analysis Technique that statistically combines the results of quantitative studies to provide a more precise effect of the results Aims for exhaustive, comprehensive searching. May use funnel plot to assess completeness Quality assessment may determine inclusion/exclusion and/or sensitivity analyses Graphical and tabular with narrative commentary Numerical analysis of measures of effect assuming absence of heterogeneity
Mixed Studies Review / Mixed Methods Review Refers to any combination of methods where one significant component is a literature review (usually systematic). Within a review context it refers to a combination of review approaches for example combining quantitative with qualitative research or outcome with process studies Requires either very sensitive search to retrieve all studies or separately conceived quantitative and qualitative strategies Requires either a generic appraisal instrument or separate appraisal processes with corresponding checklists Typically both components will be presented as narrative and in tables. May also employ graphical means of integrating quantitative and qualitative studies Analysis may characterise both literatures and look for correlations between characteristics or use gap analysis to identify aspects absent in one literature but missing in the other
Overview Generic term: summary of the [medical] literature that attempts to survey the literature and describe its characteristics May or may not include comprehensive searching (depends whether systematic overview or not) May or may not include quality assessment (depends whether systematic overview or not) Synthesis depends on whether systematic or not. Typically narrative but may include tabular features Analysis may be chronological, conceptual, thematic, etc.
Qualitative Systematic Review / Qualitative Evidence Synthesis Method for integrating or comparing the findings from qualitative studies. It looks for ‘themes’ or ‘constructs’ that lie in or across individual qualitative studies May employ selective or purposive sampling Quality assessment typically used to mediate messages not for inclusion/exclusion Qualitative, narrative synthesis Thematic analysis, may include conceptual models
Rapid Review Assessment of what is already known about a policy or practice issue, by using systematic review methods to search and critically appraise existing research Completeness of searching determined by time constraints Time-limited formal quality assessment Typically narrative and tabular Quantities of literature and overall quality/direction of effect of literature
Scoping Review Preliminary assessment of potential size and scope of available research literature. Aims to identify nature and extent of research evidence (usually including ongoing research) Completeness of searching determined by time/scope constraints. May include research in progress No formal quality assessment Typically tabular with some narrative commentary Characterizes quantity and quality of literature, perhaps by study design and other key features. Attempts to specify a viable review
State-of-the-Art Review Tend to address more current matters in contrast to other combined retrospective and current approaches. May offer new perspectives on issue or point out area for further research Aims for comprehensive searching of current literature Aims for comprehensive searching of current literature Typically narrative, may have tabular accompaniment Current state of knowledge and priorities for future investigation and research
Systematic Review Seeks to systematically search for, appraise and synthesis research evidence, often adhering to guidelines on the conduct of a review Aims for exhaustive, comprehensive searching Quality assessment may determine inclusion/exclusion Typically narrative with tabular accompaniment What is known; recommendations for practice. What remains unknown; uncertainty around findings, recommendations for future research
Systematic Search and Review Combines strengths of critical review with a comprehensive search process. Typically addresses broad questions to produce ‘best evidence synthesis’ Aims for exhaustive, comprehensive searching May or may not include quality assessment Minimal narrative, tabular summary of studies What is known; recommendations for practice. Limitations
Systematized Review Attempt to include elements of systematic review process while stopping short of systematic review. Typically conducted as postgraduate student assignment May or may not include comprehensive searching May or may not include quality assessment Typically narrative with tabular accompaniment What is known; uncertainty around findings; limitations of methodology
Umbrella Review Specifically refers to review compiling evidence from multiple reviews into one accessible and usable document. Focuses on broad condition or problem for which there are competing interventions and highlights reviews that address these interventions and their results Identification of component reviews, but no search for primary studies Quality assessment of studies within component reviews and/or of reviews themselves Graphical and tabular with narrative commentary What is known; recommendations for practice. What remains unknown; recommendations for future research

Develop a Searchable Question

When developing a searchable question, it helps to identify the key concepts of your research proposal. A clear and precise search question can be used to develop search terms during the literature searching process.

There are a number of frameworks available to use to help you break your question into its key concepts. Take a look at the frameworks below. 

  • Evidence-Based Practice
  • General Health
  • Health Management

From BMJ Best Practice :

The PICO (Population, Intervention, Comparator and Outcomes) model captures the key elements and is a good strategy to provide answerable questions.

Population : who are the relevant patients or the target audience for the problem being addressed?      Example: In women with non-tubal infertility

Intervention : what intervention is being considered?     Example: …would intrauterine insemination…

Comparator : what is the main comparator to the intervention that you want to assess?      Example: …when compared with fallopian tube sperm perfusion…

Outcomes : what are the consequences of the interventions for the patient? Or what are the main outcomes of interest to the patient or decision maker?      Example: …lead to higher live birth rates with no increase in multiple pregnancy, miscarriage or ectopic pregnancy rates?

How to clarify a clinical question. (n.d.). BMJ Best Practice . Retrieved October 26, 2022, from https://bestpractice.bmj.com/info/us/toolkit/learn-ebm/how-to-clarify-a-clinical-question/

From "Formulating the Evidence Based Practice Question":

Setting : What is the context for the question? The research evidence should reflect the context or the research findings may not be transferable.

Perspective : Who are the users, potential users, or stakeholders of the service?

Intervention : What is being done for the users, potential users, or stakeholders?

Comparison : What are the alternatives? An alternative might maintain the status quo and change nothing.

Evaluation : What measurement will determine the intervention’s success? In other words, what is the result?

Davies, K. S. (2011). Formulating the Evidence Based Practice Question: A Review of the Frameworks. Evidence Based Library and Information Practice , 6 (2), Article 2. https://doi.org/10.18438/B8WS5N

From "How CLIP became ECLIPSE":

Expectation —what does the search requester want the information for (the original ‘I’s)? Client Group Location Impact:  what is the change in the service, if any, which is being looked for? What would constitute success? How is this being measured? Professionals Service:  for which service are you looking for information? For example, outpatient services, nurse-led clinics, intermediate care

Wildridge, V., & Bell, L. (2002). How CLIP became ECLIPSE: A mnemonic to assist in searching for health policy/management information. Health Information & Libraries Journal , 19 (2), 113–115. https://doi.org/10.1046/j.1471-1842.2002.00378.x

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Study Protocol

Evaluating variable selection methods for multivariable regression models: A simulation study protocol

Roles Conceptualization, Methodology, Software, Visualization, Writing – original draft, Writing – review & editing

Affiliation Institute of Clinical Biometrics, Center for Medical Data Science, Medical University of Vienna, Vienna, Austria

ORCID logo

Roles Conceptualization, Funding acquisition, Methodology, Supervision, Writing – original draft, Writing – review & editing

Roles Writing – review & editing

Affiliation Institute of Biometry and Clinical Epidemiology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany

Roles Software, Writing – review & editing

Affiliations Institute of Clinical Biometrics, Center for Medical Data Science, Medical University of Vienna, Vienna, Austria, Austrian Agency for Health and Food Safety (AGES), Vienna, Austria

* E-mail: [email protected]

¶ Membership list can be found in the Acknowledgments section.

  • Theresa Ullmann, 
  • Georg Heinze, 
  • Lorena Hafermann, 
  • Christine Schilhart-Wallisch, 
  • Daniela Dunkler, 
  • for TG2 of the STRATOS initiative

PLOS

  • Published: August 9, 2024
  • https://doi.org/10.1371/journal.pone.0308543
  • Peer Review
  • Reader Comments

Table 1

Researchers often perform data-driven variable selection when modeling the associations between an outcome and multiple independent variables in regression analysis. Variable selection may improve the interpretability, parsimony and/or predictive accuracy of a model. Yet variable selection can also have negative consequences, such as false exclusion of important variables or inclusion of noise variables, biased estimation of regression coefficients, underestimated standard errors and invalid confidence intervals, as well as model instability. While the potential advantages and disadvantages of variable selection have been discussed in the literature for decades, few large-scale simulation studies have neutrally compared data-driven variable selection methods with respect to their consequences for the resulting models. We present the protocol for a simulation study that will evaluate different variable selection methods: forward selection, stepwise forward selection, backward elimination, augmented backward elimination, univariable selection, univariable selection followed by backward elimination, and penalized likelihood approaches (Lasso, relaxed Lasso, adaptive Lasso). These methods will be compared with respect to false inclusion and/or exclusion of variables, consequences on bias and variance of the estimated regression coefficients, the validity of the confidence intervals for the coefficients, the accuracy of the estimated variable importance ranking, and the predictive performance of the selected models. We consider both linear and logistic regression in a low-dimensional setting (20 independent variables with 10 true predictors and 10 noise variables). The simulation will be based on real-world data from the National Health and Nutrition Examination Survey (NHANES). Publishing this study protocol ahead of performing the simulation increases transparency and allows integrating the perspective of other experts into the study design.

Citation: Ullmann T, Heinze G, Hafermann L, Schilhart-Wallisch C, Dunkler D, for TG2 of the STRATOS initiative (2024) Evaluating variable selection methods for multivariable regression models: A simulation study protocol. PLoS ONE 19(8): e0308543. https://doi.org/10.1371/journal.pone.0308543

Editor: Suyan Tian, The First Hospital of Jilin University, CHINA

Received: February 7, 2024; Accepted: July 25, 2024; Published: August 9, 2024

Copyright: © 2024 Ullmann et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: This manuscript is a protocol of a simulation study. We intend to share the software code after the study has been conducted and published. This will allow recreating our data and reproducing our simulation study.

Funding: This research was funded in part by the Austrian Science Fund (FWF, https://www.fwf.ac.at/en/ ) [I-4739-B] (for T.U. and C.W.) and by the German Research Foundation (DFG, https://www.dfg.de/en ) [RA 2347/8-1] (for L. H.). For open access purposes, the author has applied a CC BY public copyright license to any author accepted manuscript version arising from this submission. The funders did not and will not have any role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

1 Introduction

Data-driven variable selection is frequently performed when modeling the associations between an outcome and multiple independent variables (sometimes also referred to as explanatory variables, covariates or predictors). Variable selection may help to generate parsimonious and interpretable models, and may also yield models with increased predictive accuracy. Despite these potential advantages, data-driven variable selection can also have unintended negative consequences that many researchers are not fully aware of. Variable selection induces additional uncertainty in the estimation process and may cause biased estimation of regression coefficients, model instability (i.e., models that are not robust with respect to small perturbations of the data set), and issues with post-selection inference such as underestimated standard errors and invalid confidence intervals [ 1 – 5 ].

A recent review [ 1 ] provided guidance about variable selection and gave an overview of possible consequences of variable selection. However, there are few systematic simulation studies that compare different variable selection methods with respect to their consequences for the resulting models (for some exceptions, see [ 6 – 10 ]). While many articles proposing new variable selection methods include a comparison with existing methods (based on simulated or real data), these comparisons are typically somewhat limited, often comparing the new method to only one to three competitors, even though there are many more existing methods. Moreover, these articles are inherently biased towards demonstrating superiority of the new methods. In particular, such studies cannot be considered as neutral . A neutral comparison study is a study whose authors do not have a vested interest in one of the competing methods, and are (as a group) approximately equally familiar with all considered methods [ 11 , 12 ]. More neutral comparison studies about existing variable selection methods are needed to better understand their properties, a viewpoint that aligns with the goals of the STRATOS initiative (STRengthening Analytical Thinking for Observational Studies [ 13 ]). The STRATOS initiative is an international consortium of biostatistical experts, and aims to provide guidance in the design and analysis of observational studies for specialist and non-specialist audiences. This perspective motivates our comprehensive simulation study.

We will focus on descriptive modeling (i.e., describing the relationship between the outcome and the independent variables in a parsimonious manner) and predictive modeling (i.e., predicting the outcome as accurately as possible) [ 14 ]. Our setting is multivariable regression analysis with one outcome variable. The outcome is either continuous (linear regression) or binary (logistic regression). We simulate data in a low-dimensional scenario (20 variables consisting of 10 true predictors and 10 noise variables). Different variable selection methods with multiple parameter settings are compared: forward selection, stepwise forward selection, backward elimination, augmented backward elimination [ 15 ], univariable selection, univariable selection followed by backward elimination, the Lasso [ 16 ], the relaxed Lasso [ 9 , 17 ], and the adaptive Lasso [ 18 ]. We compare the performances of these methods with respect to false inclusion and/or exclusion of variables, consequences on bias and variance of the estimated regression coefficients, the validity of the confidence intervals for the coefficients, the accuracy of the estimated variable importance ranking, and finally the predictive performance of the selected models.

Using simulated instead of real data allows us to a) know the true data generating process and b) systematically vary several data characteristics [ 19 , 20 ]. For example, we will include varying sample sizes and R 2 , as the consequences of variable selection depend on these parameters. To ensure that the simulation results are practically relevant, we use real data as the starting point for our simulation. The distributions and correlation structure of the variables are based on data from the National Health and Nutrition Examination Survey (NHANES) [ 21 ]. The choice of variables and true regression coefficients is inspired by an applied study about predicting the difference between ambulatory/home and clinic blood pressure readings [ 22 ]. Our simulated data thus mimics real cardiovascular data.

Our focus is on low-dimensional data, which is reflected in our simulation setting with twenty independent variables. Data of this type frequently appears in medicine and other application fields, and researchers often apply variable selection in this context. For example, a systematic review of models for COVID-19 prognosis [ 23 , 24 ] identified 236 newly developed regression models for prediction. Data-driven variable selection was applied (and reported) for 196 models. In 165 models both the number of candidate predictors (i.e., the predictors considered at the start of data-driven selection) and the number of predictors in the final model were reported; the median numbers were 28 (range 4–130), and 6 (range 1–38), respectively. This demonstrates that low- to medium-dimensional data played an important role in COVID-19 prediction research. Of course, data-driven variable selection is also relevant for high-dimensional data. Comparing variable selection methods for high-dimensional data would require a different study design and is not the purpose of this planned simulation study.

As mentioned above, neutrality is an important goal when conducting systematic comparison studies. “Perfect” neutrality may be the ultimate goal, but this ideal can be difficult to achieve in practice. While we aim to be as neutral as possible, we disclose (for the purpose of full transparency) that one of the methods for variable selection included in our comparison, namely augmented backwards elimination, was originally proposed by two authors of the present study protocol [ 15 ]. Our goal was to not let this fact influence our choice of study design, though unconscious biases can never be fully excluded. Striving for as much neutrality as possible motivated us to publish this study protocol. This will allow us to integrate the comments of reviewers before performing the simulation. For the design of our study, results from previous smaller simulation studies and pilot studies were taken into account [ 1 ]; however, the study outlined in this protocol has not yet been run and analyzed. Preregistration of study protocols for simulation studies/methodological studies is still very rare (for an exception, see [ 25 ]). However, this practice could offer similar advantages to those discussed for preregistration in applied research, such as increased transparency and prevention of “hindsight bias” [ 26 ]. Potential advantages of preregistering protocols for simulation studies, but also possible limitations and challenges, are discussed more extensively elsewhere [ 27 ].

A specific goal of our simulation study is to evaluate previously published recommendations about variable selection [ 1 ], which we discuss in Section 2. We then describe our simulation design in Section 3, explain the planned code review in Section 4, and conclude the protocol with some final remarks in Section 5.

2 Previous variable selection recommendations

Varied viewpoints exist in the literature as to whether researchers should apply data-driven variable selection, and, if so, which methods and parameters are deemed preferable. Some authors generally caution against data-driven variable selection, stressing potential negative consequences [ 5 ]. Other authors put more focus on potential advantages of variable selection and are more optimistic about using selection methods, at least if the sample size is large enough and if selection is accompanied by a stability analysis [ 28 ]. In a review conducted by three co-authors of the present study protocol, Heinze et al. [ 1 ] summarized different perspectives from the literature. Drawing upon existing recommendations, but also taking their own experience and a small simulation study into account, they derived recommendations for the usage of variable selection methods. These recommendations consider both benefits and drawbacks of variable selection, thereby reconciling different viewpoints on the matter. The recommendations depend on the “events-per-variable” (EPV) in the data. The EPV is the ratio between sample size (in linear regression) or the number of the less frequent outcome (in logistic regression) and the number of independent variables. Data-driven variable selection is applied on a carefully designed “global” model which includes all independent variables relevant for the research question. The denominator of EPV refers to the number of design variables (including possible dummy variables and other constructed variables) in this global model. The following bullet points list the recommendations, and how we plan to evaluate them.

  • EPV > 25: While variable selection may generally work well for a large EPV value, the selection of independent variables with small effect size can still be unstable. If backward elimination is used, a stringent threshold of α = 0.05 or selection with the BIC may lead to a more accurate selection of variables than milder thresholds. In our study : We will check whether selection rates of variables with small standardized regression coefficients (e.g., ±0.25) are notably different from either 0 or 1 (which indicates instability). For backward elimination, we will evaluate whether the selection of variables is more accurate when using the threshold α = 0.05 or the BIC (which corresponds to even stricter thresholds for our considered sample sizes [ 1 ]), compared to using larger α values.
  • 10 < EPV ≤ 25: In general, the selection of variables might be unstable with such an EPV. When variables with unclear effect size are selected, their effects might be over-estimated. Penalized estimation (Lasso) or postestimation shrinkage is thus recommended. If backward elimination is used, a threshold corresponding to selection with the AIC (approximately α = 0.157) is recommended, but not smaller α values. In our study : Again, we will evaluate stability by checking whether selection rates of variables, particularly those with small standardized regression coefficients, are notably different from either 0 or 1. We will also calculate the conditional bias (i.e., bias conditioned on selection) of the variables and analyze whether variables with small standardized regression coefficients have large conditional bias away from zero. For backward elimination, we will evaluate to which extent a threshold of α = 0.157 (or an even milder threshold of α = 0.5) selects the true predictors more frequently than smaller thresholds (i.e., a fixed threshold of α = 0.05 or selection with the BIC) [ 3 ].
  • EPV ≤ 10: Data-driven variable selection is generally not recommended. In our study : We will analyze whether variable selection has negative consequences with respect to the different performance criteria.

The results of variable selection are not only influenced by EPV, but also by other aspects such as the R 2 of the model. We will thus consider different R 2 values in our simulation study. The recommendations above do not take R 2 into account, as the R 2 of the model is typically not known prior to the data analysis.

3 Simulation design

Morris et al. [ 19 ] proposed to describe the following components when reporting a simulation study: the aims of the study (A), the data-generating mechanisms (D), the estimands (i.e., the population quantities which are estimated) and other targets of interest (E), the methods to be compared (M), and the performance measures used for evaluating the methods (P). The ADEMP components of our study are briefly summarized in Tables 1 and 2 . We now describe the components in more detail.

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3.1 Aims (A)

We aim to compare different variable selection methods for multivariable linear or logistic regression, with respect to their consequences for the resulting models. We consider consequences on bias and variance of the estimated regression coefficients, validity of confidence intervals for the coefficients, false inclusion or exclusion of variables, and predictive performance. We analyze the behavior of variable selection methods…

  • … depending on sample size/EPV, with particular focus on evaluating the recommendations of Heinze et al. [ 1 ],
  • … depending on the R 2 of the population model,
  • … depending on the modeling goal (description or prediction),
  • … when functional forms are misspecified (i.e., when fitting models assuming linear functional forms of continuous predictors even though the true functional forms are nonlinear),
  • … when switching from our realistic scenario that mimics cardiovascular data to simplified scenarios (i.e., all variables are normally distributed and/or uncorrelated).

3.2 Data-generating mechanisms (D)

3.2.1 simulation of independent variables (predictors and noise variables)..

We simulate 20 independent variables: 10 true predictors (from now on just called “predictors”) and 10 noise variables. The correlation structure and distributions are based on real-world data from the 2013–14 and 2015–2016 cycles of the National Health and Nutrition Examination Survey (NHANES) [ 21 ]. To choose suitable variables in the NHANES data, we drew inspiration from a regression model reported by Sheppard et al. [ 22 ] for predicting the difference between diastolic blood pressure readings as measured ambulatory/at home versus in the clinic. The variables are described in detail in S1 Appendix . The correlation matrix Σ for the simulation is based on the empirical correlation matrix of the variables. For better interpretability, we set correlations below 0.15 to zero and round all values to the closest multiple of 0.05 (see S1 Fig and S1 Table for the resulting correlation matrix).

To obtain distributions from the NHANES data, we fit Bernoulli distributions for the binary variables, and normal distributions, log-normal distributions, or approximations of the empirical cumulative distribution function (CDF) for the continuous variables. For each continuous variable, we truncate its distribution with the minimum of the variable in the NHANES data as the lower bound and the maximum as the upper bound. The resulting distributions are as follows (see also Fig 1 ):

  • predictors: X 1 (log-normal), X 2 (continuous with approximated CDF), X 3 (log-normal), X 4 (binary, p = 0.50), X 5 (normal), X 6 (binary, p = 0.29), X 7 (log-normal), X 8 (log-normal), X 9 (normal), X 10 (binary, p = 0.11)
  • noise variables: X 11 (log-normal), X 12 (normal), X 13 (log-normal), X 14 (binary, p = 0.61), X 15 (normal), X 16 (binary, p = 0.20), X 17 (log-normal), X 18 (normal), X 19 (normal), X 20 (binary, p = 0.20)

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Predictors are ordered by absolute values of standardized regression coefficients. Histograms are based on a large simulated dataset ( n = 100, 000).

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The distributions, together with the correlation matrix Σ, are then used as input for the normal-to-anything (NORTA) method for simulation [ 29 , 30 ].

3.2.2 Choice of regression coefficients.

literature review on previous studies

This choice reflects a mixture of stronger and weaker effects, a situation typical for many applications in biology and medicine. We would expect different behaviors of the predictors during variable selection depending on their effects.

literature review on previous studies

The regression coefficients for the noise variables X 11 , …, X 20 are set to zero.

literature review on previous studies

3.2.3 Simulation of outcome Y .

The outcome Y is simulated as follows:

literature review on previous studies

3.2.4 Nonlinear functional forms.

So far, we assumed that the functional forms of the effects of continuous predictors on Y are linear. In applied studies in biology and medicine, the actual functional forms of such variables might often be nonlinear, but researchers nonetheless fit a model with linear functional forms, e.g., because they are not aware that some functional forms might be nonlinear, or because they prefer a simpler model. To analyze the behavior of variable selection methods in this scenario, we include settings 1b-7b (corresponding to settings 1–7) where all predictors have nonlinear functional forms. The models that we consider for analysing the simulated data (linear/logistic regression) will not take the nonlinear functional forms into account and will thus be misspecified.

For each continuous predictor X j , we define a function g j ( x ) that describes the nonlinear functional form of the effect of the predictor on Y . We choose various functional forms: quadratic, log-quadratic, exponential and sigmoid. The functions are depicted in S3 Fig ; exact definitions are given in S1 Appendix .

literature review on previous studies

After determining β ( g ) , the outcome Y is simulated as previously described in Section 3.2.3, with xβ replaced by the nonlinear composite predictor.

literature review on previous studies

https://doi.org/10.1371/journal.pone.0308543.t003

For the global model in the settings with nonlinear effects, we will not only calculate the usual standard errors of the regression coefficients, but also robust standard errors [ 31 ], to check whether robust SEs improve the coverage of the confidence intervals. If robust SEs improve the coverage for the global model, it would be interesting to analyze whether this is also the case for models obtained by variable selection; however, combining robust standard errors with variable selection requires some further work and would go beyond the scope of the proposed study. For now, we will restrict the investigation of robust SEs to the global model for linear regression.

3.2.5 Simplified settings.

While our main focus is on simulating variables of various distribution types (e.g., Bernoulli, normal, and log-normal) and with correlation matrix Σ based on the empirical correlation matrix from the NHANES data ( S1 Table ), we are also interested in the behavior of the variable selection methods for data with simpler distribution-correlation structures. We thus consider the three following simplified scenarios:

literature review on previous studies

  • The variables have the same individual distributions as described in Section 3.2.1 ( Fig 1 ), but are not correlated.

literature review on previous studies

Depending on the results for settings 1b-2b and 4b-7b with nonlinear effects, we might additionally consider nonlinear effects for the simplified scenario 3 (variables not multivariate normal and not correlated).

3.2.6 Sample sizes.

For linear regression, we consider eight different sample sizes: 100, 200, 400, 500, 800, 1600, 3200, and 6400. These sample sizes result when doubling sample size six times from 100. Additionally, the sample size 500 is included because it corresponds to EPV = 25, and this EPV value was specifically mentioned in the recommendations of Heinze et al. [ 1 ].

literature review on previous studies

Because this procedure is unstable for small event rates, we do not use the alignment based on standard errors for event rate 0.05. Instead, we choose sample sizes corresponding to the EPV values in linear regression.

The resulting sample sizes are displayed in Table 4 . The numbers below the sample sizes indicate the corresponding EPV values. For event rate 0.05, we will first include sample sizes only up to 10,000 (EPV = 25) to save computation time. We expect the variable selection methods to behave similarly for both event rates (0.3 and 0.05). If we observe different behaviors for event rate 0.05, we will include the additional sample sizes.

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In S1 Appendix , we additionally report expected shrinkage factors for each setting, based on sample size and R 2 [ 32 , 33 ].

3.3 Estimands and other targets (E)

As estimands, we consider the true regression coefficients of the data generating models. As further targets, we are interested in model selection (e.g., whether the true model is selected) and predictive performance of the selected models.

For the settings with linear functional forms, the regression coefficient estimands are the coefficients β (respectively c β for logistic regression) as described in Sections 3.2.2 and 3.2.3. For the settings with nonlinear effects, we cannot take the coefficients β ( g ) as defined in 3.2.4 as estimands, because our linear/logistic regression models will not take nonlinear functional forms into account and will thus be misspecified.

literature review on previous studies

3.4 Methods (M)

3.4.1 overview of variable selection methods..

We include the following methods:

  • Forward selection with AIC: starting from the model containing only the intercept, variables are iteratively added to the model based on their capability to decrease the AIC when included.
  • Stepwise forward selection with AIC (i.e., forward selection with backward elimination steps): like simple forward selection, this method starts from the intercept model and adds variables based on the AIC. However, in each step, re-exclusion of already selected variables is allowed, based on the capability to decrease the AIC when removed.
  • Backward elimination with α = 0.05, with BIC, with AIC, and with α = 0.5: starting from the global model, variables are iteratively removed, either based on their capability to decrease the BIC/AIC when removed, or based on the p -values of their coefficients. We do not consider a stepwise variant of backward elimination with forward selection steps, following the recommendations of Royston and Sauerbrei [ 28 , p. 32] who argue that allowing re-inclusion of removed variables in backward elimination is rarely relevant, while allowing re-exclusion of included variables may cause a notable difference for forward selection.
  • Augmented backward elimination (ABE) with AIC [ 15 ]: backward elimination is combined with the change-in-estimate criterion [ 34 , 35 ]. A variable that would be removed in backward elimination based on AIC may stay in the model if its removal would induce a large change in the estimated regression coefficients of the other variables that are currently in the model. As threshold for the standardized change-in-estimate, we choose τ = 0.05. We will use the R package abe [ 36 ].
  • Univariable selection with α = 0.05 and α = 0.20: a variable is selected if its regression coefficient in a univariable model is significant at level α . While many authors have advised against using univariable selection [ 5 , 37 , 38 ], the method is still often used in practice, which is why we include it in our simulation study.
  • Univariable selection with α = 0.20, followed by backward elimination with α = 0.05: frequently, researchers use this combination instead of using only univariable selection or only backward elimination [ 39 , 40 ] However, the warnings against univariable selection still apply to the combination method.
  • Lasso [ 16 ]: a penalty on the coefficients is added to the OLS criterion (linear regression) or the negative log-likelihood (logistic regression), causing shrinkage of the coefficients toward zero and setting some of them to exactly zero.
  • Relaxed Lasso [ 9 , 17 ]: variables are selected with the Lasso, but the shrinkage of the coefficients of the selected variables is relaxed by refitting the model with the selected variables without penalty.
  • Adaptive Lasso [ 18 ]: first, the global linear/logistic model is fit, then a Lasso with variable-specific weights for the penalty is estimated. The estimates from the first step serve to get the variable-specific weights for the second step: the weights are calculated such that a variable with larger regression coefficient in the first step is penalized less than a variable with smaller regression coefficient. For all variants of the Lasso, we will use the R package glmnet [ 41 ]. The complexity parameter λ will be tuned with 10-fold cross-validation (CV). As performance criterion for the prediction on test sets during CV, we use the mean squared error for linear regression and deviance for logistic regression. For the relaxed Lasso, we additionally consider tuning λ with the BIC.

We also consider the global model with all variables.

3.4.2 Firth correction in logistic regression.

In the models for logistic regression, separation may occur (i.e., perfect separation of events and non-events by a linear combination of covariates), particularly for small to medium sample sizes and low event rates [ 42 ]. In this case, at least one parameter estimate is infinite. While separation can be detected by linear programming [ 43 ], we found that in practice, a simple and robust check can be performed by inspecting the model standard errors of the regression coefficients. If at least one standard error is extremely large, this indicates separation. A possible solution to the problem of separation is to apply the Firth correction to obtain finite parameter estimates [ 42 , 44 ].

In the simulation settings for logistic regression, we check for each individual simulated dataset whether separation occurs. In the case of separation, we apply the Firth correction (with the FLIC intercept correction [ 45 ] to obtain unbiased predictions), otherwise we use the standard logistic regression. When Firth correction is applied, confidence intervals for the regression coefficients are calculated based on the profile penalized likelihood, otherwise based on the profile likelihood.

We describe our procedure to check for separation based on the model standard errors of the coefficients in S1 Appendix .

3.5 Performance measures (P)

We organize the performance measures into three categories, based on which estimands/targets they pertain to. Formulas for all performance measures are given in S1 Appendix .

literature review on previous studies

Performance measures for model selection as target include the selection rate of the true model consisting exactly of the ten predictors, the selection rate of an “over-selection” model which we define as a model including all predictors as well as at least one noise variable (previously called an “inflated” model [ 15 ]), and the selection rate of any “under-selection” model defined as a model not containing all predictors but possibly including noise variables (previously called a “biased” model [ 15 ]).

literature review on previous studies

The performance measures for the regression coefficients and for model selection are primarily relevant for descriptive models, while performance measures for predictive performance are mainly relevant for prediction models. However, a descriptive model may also be suitable for prediction; therefore, performance measures for prediction could also be relevant for descriptive modeling. Vice versa, in prediction models, aspects such as interpretability, fairness etc. often play an important role; researchers might thus consider performance measures such as bias of coefficients also for prediction models.

3.6 Monte Carlo errors and number of simulation runs

literature review on previous studies

4 Code review

To ensure reproducibility, as well as readability, the code will be checked by another researcher (a “code reviewer”) who works at the same institute as the first, second and last author of this protocol, but was not involved in planning the study. After writing the code, the first author (T.U.) will hand over the code to the code reviewer, together with instructions for running the code as well as some partial results (using less than the full n sim = 2000 repetitions). The code reviewer will then check the plausibility of the partial results and provide feedback on the simulation code, focusing on a) data generation, b) the implementation of the compared models, and c) the implementation of the performance measures applied to these models. Once T.U. and the code reviewer have agreed upon a final version of the code, T.U. will re-run the partial results, and the code reviewer will check the complete computational reproducibility by re-running the code on another machine. This check for reproducibility is done on the partial results as the generation of the final results is expected to require large amounts of computational resources. Once the reproducibility check has successfully concluded, T.U. will perform the full n sim = 2000 repetitions to generate the final results.

5 Final remarks

Our simulation study will enable researchers to better understand the consequences of variable selection, and will clarify differences in the performance of different selection methods depending on the considered scenarios. To make the results of the study more accessible and interpretable, we plan to display all results in an interactive web app (Shiny app) that will be published alongside the main paper. We will also make our code available on a Git repository, and will specify random seeds to ensure reproducibility of the results.

The performance measures for our study (Section 3.5) are defined as expected values and probabilities. Their estimation by simulation thus always involves taking the mean over (a part of) the simulation repetitions. However, if one only calculates the mean over the repetitions, one might miss relevant properties of the distribution of the values over the simulation repetitions. We will thus use distribution plots and correlation analyses to evaluate the simulation results in more detail [ 19 ]. Moreover, we will analyze how many variables were selected by each variable selection method. We did not include model size as a performance measure in Section 3.5 because there is no clear target value and smaller/larger values are not automatically better/worse (a smaller model size is preferable in some applications, but might be less relevant in others). A specific focus on model size (e.g., comparing different variable selection methods under constraints w.r.t. the number of chosen variables) would require a different study design.

literature review on previous studies

In future work, it would be interesting to consider various extensions of our simulation. For example, while we focus on linear and logistic regression in the present protocol, data-driven variable selection is also often used in the context of survival analysis. We plan to conduct a further simulation study comparing different data-driven variable selection methods for Cox regression and the accelerated failure time model.

In the present study, we include several settings where all predictors have true nonlinear functional forms, but we nevertheless fit all models with linear functional forms; this mimics the frequent misspecification of models in practice. Generally, when fitting a regression model with linear effects, it is advisable to check for misspecification by analyzing the residuals. If misspecification is only mild, then a model with linear effects might still be justifiable. If misspecification is too severe, functional form selection can be performed to account for nonlinear effects, e.g., with spline-based approaches. In future work, our study could be extended by considering the combination of variable selection and functional form selection, which is a complex issue [ 39 ].

We focus on low-dimensional data in our study. Future studies could compare variable selection methods for high-dimensional data. Finally, our study considers variable selection in a frequentist framework. Future simulation studies could also evaluate Bayesian methods for variable selection.

Supporting information

S1 fig. correlation network graph..

https://doi.org/10.1371/journal.pone.0308543.s001

S2 Fig. Absolute standardized regression coefficients plotted against coefficients of determination for each independent variable.

https://doi.org/10.1371/journal.pone.0308543.s002

S3 Fig. Nonlinear effects.

https://doi.org/10.1371/journal.pone.0308543.s003

S1 Appendix. Details of the simulation design.

https://doi.org/10.1371/journal.pone.0308543.s004

S1 Table. Correlation table.

https://doi.org/10.1371/journal.pone.0308543.s005

Acknowledgments

We would like to thank the members of Topic Group (TG) 2 and the Publications Panel of the STRengthening Analytical Thinking for Observational Studies (STRATOS) initiative for helpful comments. In particular, we thank Willi Sauerbrei, Frank Harrell, Nadja Klein and Harald Binder.

At the time of submission, STRATOS TG2 consisted of the following members (in alphabetical order): Michal Abrahamowicz, Harald Binder, Daniela Dunkler, Frank Harrell, Georg Heinze, Marc Henrion, Michael Kammer, Aris Perperoglou, Willi Sauerbrei, and Matthias Schmid. The group is co-chaired by Georg Heinze ( [email protected] ), Aris Perperoglou, and Willi Sauerbrei.

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Purdue University Graduate School

Informing Educator Preparation Programs_Daniela Vilarinho Rezende Pereira

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Informing Educator Preparation Programs: Insights into Technology Integration

The overarching purpose of this three-paper dissertation was to investigate the affordances of technology in educational settings and gain insight into how preservice and inservice teachers integrate technology as they design, develop, implement, and manage learning experiences. To meet this goal, three studies were conducted. In study 1 the purpose was to describe how preservice teachers identify educational problems and suggest solutions in which educational technology can be meaningfully implemented by using a problem-solving lens. Participated in this study 100 preservice teachers enrolled in an introductory educational technology course. Students’ technology integration activity was analyzed for this study. This activity, divided into three parts, required that students (1) shared and reflected on their best academic learning experience, (2) described how they could integrate technology into that learning experience, and (3) revisited their suggestions for technology integration, evaluated their ideas, and suggested revisions. Data were analyzed using an ill-structured problem-solving model synthesized from previous literature: identifying problems, generating solutions, making justifications, and monitoring. Results of this study indicated that preservice teachers had a simplistic understanding of technology integration, likely resulting from underdeveloped problem-solving skills. In study 2 the purpose was to identify the instructional strategies and technology affordances used while integrating technology that facilitated the development of student creativity by completing a systematic literature review about how technology (i.e., social media) is being used by educators to foster creativity. After the process of identification and screening, a total of 27 articles met the inclusion criteria and were selected for further analysis. The results indicated that, in most studies in which the use of technology was associated with promoting student creativity, a student-centered approach was used. Students had autonomy and flexibility to produce content, express their opinions, and share their experiences using social media. Also, participants used social media to create their own products, communicate with others, and collaborate virtually. In the studies, we identified that the social media affordances of ownership, association, and visibility lead to fostering student creativity. In conclusion, social media, when integrated with appropriate instructional strategies, can be successfully used as an educational tool to build an environment that promotes student creativity. In study 3 the purpose was to analyze the forms in which special education teachers design learning experiences that provide an environment for creativity development for students from special education and how their proposed technology integration plays a role in it across different settings (i.e., face-to-face, blended, and online learning). Three practicing teachers enrolled in an online graduate program in special education participated in this study. For the purpose of this study, the primary data source consisted of assignments (i.e., artifacts and reflections) submitted by students to the Technology Integration - Blended and Online Teaching (Ti-BOT) program, a licensure required as part of their Special Education program. Artifacts were analyzed through the lens of the existing literature on learning environments for creativity. Reflections were analyzed using a thematic analysis approach, applying a combination of inductive and deductive coding. The artifacts presented by the participants included elements of a creative environment and technology often facilitated the development of such an environment. However, the participants did not appear to explicitly and intentionally design activities to foster creativity, but to make modifications to learning activities and assessments that reflected the level of individualization and adaptations that are typically expected from special education teachers, described in individualized education plans (IEPs), and guided by Universal Design for Learning (UDL) principles. With the findings from this three-paper dissertation, the goal is to provide recommendations for how educator preparation programs can improve how they are approaching technology integration, gain deeper understanding of technology integration across diverse contexts and tools, and offer strategies for supporting the deeper consideration of how technologies can be meaningfully used.

Degree Type

  • Doctor of Philosophy
  • Curriculum and Instruction

Campus location

  • West Lafayette

Advisor/Supervisor/Committee Chair

Additional committee member 2, additional committee member 3, additional committee member 4, additional committee member 5, usage metrics.

  • Curriculum and pedagogy not elsewhere classified

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  27. Informing Educator Preparation Programs: Insights into Technology

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  28. A novel variant in the SPTB gene underlying hereditary spherocytosis

    Background Hereditary spherocytosis (HS, MIM#612641) is one of the most common hereditary hemolytic disorders. This study aimed to confirm a novel variant's pathogenicity and reveal a patient's genetic etiology. Methods The clinical data of a patient with HS who underwent genetic sequencing at the Children's Hospital of Chongqing Medical University were reviewed retrospectively. In ...

  29. Brain volumetric changes in menopausal women and its association with

    The menopausal transition has been proposed to put women at risk for undesirable neurological symptoms, including cognitive decline. Previous studies suggest that alterations in the hormonal milieu modulate brain structures associated with cognitive function. This structured review provides an overview of the relevant studies that have utilized MRI to report volumetric differences in the brain ...

  30. Sustainability

    A substantial amount of bauxite tailings (BTs) at abandoned mine sites have been stored in waste reservoirs for long periods, leading to significant land occupation and environmental degradation. Although many studies of the resource utilization of BTs were conducted to address this challenge, there is still a lack of efforts to systematically review the state of the art in BTs. In the present ...