how to make validity and reliability in research

Frequently Asked Questions

What is reliability and validity in research.

Reliability in research refers to the consistency and stability of measurements or findings. Validity relates to the accuracy and truthfulness of results, measuring what the study intends to. Both are crucial for trustworthy and credible research outcomes.

What is validity?

Validity in research refers to the extent to which a study accurately measures what it intends to measure. It ensures that the results are truly representative of the phenomena under investigation. Without validity, research findings may be irrelevant, misleading, or incorrect, limiting their applicability and credibility.

What is reliability?

Reliability in research refers to the consistency and stability of measurements over time. If a study is reliable, repeating the experiment or test under the same conditions should produce similar results. Without reliability, findings become unpredictable and lack dependability, potentially undermining the study’s credibility and generalisability.

What is reliability in psychology?

In psychology, reliability refers to the consistency of a measurement tool or test. A reliable psychological assessment produces stable and consistent results across different times, situations, or raters. It ensures that an instrument’s scores are not due to random error, making the findings dependable and reproducible in similar conditions.

What is test retest reliability?

Test-retest reliability assesses the consistency of measurements taken by a test over time. It involves administering the same test to the same participants at two different points in time and comparing the results. A high correlation between the scores indicates that the test produces stable and consistent results over time.

How to improve reliability of an experiment?

• Standardise procedures and instructions.
• Use consistent and precise measurement tools.
• Train observers or raters to reduce subjective judgments.
• Increase sample size to reduce random errors.
• Conduct pilot studies to refine methods.
• Repeat measurements or use multiple methods.
• Address potential sources of variability.

What is the difference between reliability and validity?

Reliability refers to the consistency and repeatability of measurements, ensuring results are stable over time. Validity indicates how well an instrument measures what it’s intended to measure, ensuring accuracy and relevance. While a test can be reliable without being valid, a valid test must inherently be reliable. Both are essential for credible research.

Are interviews reliable and valid?

Interviews can be both reliable and valid, but they are susceptible to biases. The reliability and validity depend on the design, structure, and execution of the interview. Structured interviews with standardised questions improve reliability. Validity is enhanced when questions accurately capture the intended construct and when interviewer biases are minimised.

Are IQ tests valid and reliable?

IQ tests are generally considered reliable, producing consistent scores over time. Their validity, however, is a subject of debate. While they effectively measure certain cognitive skills, whether they capture the entirety of “intelligence” or predict success in all life areas is contested. Cultural bias and over-reliance on tests are also concerns.

Are questionnaires reliable and valid?

Questionnaires can be both reliable and valid if well-designed. Reliability is achieved when they produce consistent results over time or across similar populations. Validity is ensured when questions accurately measure the intended construct. However, factors like poorly phrased questions, respondent bias, and lack of standardisation can compromise their reliability and validity.

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• Reliability vs Validity in Research | Differences, Types & Examples

Reliability vs Validity in Research | Differences, Types & Examples

Published on 3 May 2022 by Fiona Middleton . Revised on 10 October 2022.

Reliability and validity are concepts used to evaluate the quality of research. They indicate how well a method , technique, or test measures something. Reliability is about the consistency of a measure, and validity is about the accuracy of a measure.

It’s important to consider reliability and validity when you are creating your research design , planning your methods, and writing up your results, especially in quantitative research .

Table of contents

Understanding reliability vs validity, how are reliability and validity assessed, how to ensure validity and reliability in your research, where to write about reliability and validity in a thesis.

Reliability and validity are closely related, but they mean different things. A measurement can be reliable without being valid. However, if a measurement is valid, it is usually also reliable.

What is reliability?

Reliability refers to how consistently a method measures something. If the same result can be consistently achieved by using the same methods under the same circumstances, the measurement is considered reliable.

What is validity?

Validity refers to how accurately a method measures what it is intended to measure. If research has high validity, that means it produces results that correspond to real properties, characteristics, and variations in the physical or social world.

High reliability is one indicator that a measurement is valid. If a method is not reliable, it probably isn’t valid.

However, reliability on its own is not enough to ensure validity. Even if a test is reliable, it may not accurately reflect the real situation.

Validity is harder to assess than reliability, but it is even more important. To obtain useful results, the methods you use to collect your data must be valid: the research must be measuring what it claims to measure. This ensures that your discussion of the data and the conclusions you draw are also valid.

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Reliability can be estimated by comparing different versions of the same measurement. Validity is harder to assess, but it can be estimated by comparing the results to other relevant data or theory. Methods of estimating reliability and validity are usually split up into different types.

Types of reliability

Different types of reliability can be estimated through various statistical methods.

Types of validity

The validity of a measurement can be estimated based on three main types of evidence. Each type can be evaluated through expert judgement or statistical methods.

To assess the validity of a cause-and-effect relationship, you also need to consider internal validity (the design of the experiment ) and external validity (the generalisability of the results).

The reliability and validity of your results depends on creating a strong research design , choosing appropriate methods and samples, and conducting the research carefully and consistently.

Ensuring validity

If you use scores or ratings to measure variations in something (such as psychological traits, levels of ability, or physical properties), it’s important that your results reflect the real variations as accurately as possible. Validity should be considered in the very earliest stages of your research, when you decide how you will collect your data .

• Choose appropriate methods of measurement

Ensure that your method and measurement technique are of high quality and targeted to measure exactly what you want to know. They should be thoroughly researched and based on existing knowledge.

For example, to collect data on a personality trait, you could use a standardised questionnaire that is considered reliable and valid. If you develop your own questionnaire, it should be based on established theory or the findings of previous studies, and the questions should be carefully and precisely worded.

• Use appropriate sampling methods to select your subjects

To produce valid generalisable results, clearly define the population you are researching (e.g., people from a specific age range, geographical location, or profession). Ensure that you have enough participants and that they are representative of the population.

Ensuring reliability

Reliability should be considered throughout the data collection process. When you use a tool or technique to collect data, it’s important that the results are precise, stable, and reproducible.

• Apply your methods consistently

Plan your method carefully to make sure you carry out the same steps in the same way for each measurement. This is especially important if multiple researchers are involved.

For example, if you are conducting interviews or observations, clearly define how specific behaviours or responses will be counted, and make sure questions are phrased the same way each time.

• Standardise the conditions of your research

When you collect your data, keep the circumstances as consistent as possible to reduce the influence of external factors that might create variation in the results.

For example, in an experimental setup, make sure all participants are given the same information and tested under the same conditions.

It’s appropriate to discuss reliability and validity in various sections of your thesis or dissertation or research paper. Showing that you have taken them into account in planning your research and interpreting the results makes your work more credible and trustworthy.

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Validity & Reliability In Research

A Plain-Language Explanation (With Examples)

By: Derek Jansen (MBA) | Expert Reviewer: Kerryn Warren (PhD) | September 2023

Validity and reliability are two related but distinctly different concepts within research. Understanding what they are and how to achieve them is critically important to any research project. In this post, we’ll unpack these two concepts as simply as possible.

This post is based on our popular online course, Research Methodology Bootcamp . In the course, we unpack the basics of methodology  using straightfoward language and loads of examples. If you’re new to academic research, you definitely want to use this link to get 50% off the course (limited-time offer).

Overview: Validity & Reliability

• The big picture
• Validity 101
• Reliability 101 
• Key takeaways

First, The Basics…

First, let’s start with a big-picture view and then we can zoom in to the finer details.

Validity and reliability are two incredibly important concepts in research, especially within the social sciences. Both validity and reliability have to do with the measurement of variables and/or constructs – for example, job satisfaction, intelligence, productivity, etc. When undertaking research, you’ll often want to measure these types of constructs and variables and, at the simplest level, validity and reliability are about ensuring the quality and accuracy of those measurements .

As you can probably imagine, if your measurements aren’t accurate or there are quality issues at play when you’re collecting your data, your entire study will be at risk. Therefore, validity and reliability are very important concepts to understand (and to get right). So, let’s unpack each of them.

What Is Validity?

In simple terms, validity (also called “construct validity”) is all about whether a research instrument accurately measures what it’s supposed to measure .

For example, let’s say you have a set of Likert scales that are supposed to quantify someone’s level of overall job satisfaction. If this set of scales focused purely on only one dimension of job satisfaction, say pay satisfaction, this would not be a valid measurement, as it only captures one aspect of the multidimensional construct. In other words, pay satisfaction alone is only one contributing factor toward overall job satisfaction, and therefore it’s not a valid way to measure someone’s job satisfaction.

Oftentimes in quantitative studies, the way in which the researcher or survey designer interprets a question or statement can differ from how the study participants interpret it . Given that respondents don’t have the opportunity to ask clarifying questions when taking a survey, it’s easy for these sorts of misunderstandings to crop up. Naturally, if the respondents are interpreting the question in the wrong way, the data they provide will be pretty useless . Therefore, ensuring that a study’s measurement instruments are valid – in other words, that they are measuring what they intend to measure – is incredibly important.

There are various types of validity and we’re not going to go down that rabbit hole in this post, but it’s worth quickly highlighting the importance of making sure that your research instrument is tightly aligned with the theoretical construct you’re trying to measure .  In other words, you need to pay careful attention to how the key theories within your study define the thing you’re trying to measure – and then make sure that your survey presents it in the same way.

For example, sticking with the “job satisfaction” construct we looked at earlier, you’d need to clearly define what you mean by job satisfaction within your study (and this definition would of course need to be underpinned by the relevant theory). You’d then need to make sure that your chosen definition is reflected in the types of questions or scales you’re using in your survey . Simply put, you need to make sure that your survey respondents are perceiving your key constructs in the same way you are. Or, even if they’re not, that your measurement instrument is capturing the necessary information that reflects your definition of the construct at hand.

If all of this talk about constructs sounds a bit fluffy, be sure to check out Research Methodology Bootcamp , which will provide you with a rock-solid foundational understanding of all things methodology-related. Remember, you can take advantage of our 60% discount offer using this link.

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What Is Reliability?

As with validity, reliability is an attribute of a measurement instrument – for example, a survey, a weight scale or even a blood pressure monitor. But while validity is concerned with whether the instrument is measuring the “thing” it’s supposed to be measuring, reliability is concerned with consistency and stability . In other words, reliability reflects the degree to which a measurement instrument produces consistent results when applied repeatedly to the same phenomenon , under the same conditions .

As you can probably imagine, a measurement instrument that achieves a high level of consistency is naturally more dependable (or reliable) than one that doesn’t – in other words, it can be trusted to provide consistent measurements . And that, of course, is what you want when undertaking empirical research. If you think about it within a more domestic context, just imagine if you found that your bathroom scale gave you a different number every time you hopped on and off of it – you wouldn’t feel too confident in its ability to measure the variable that is your body weight 🙂

It’s worth mentioning that reliability also extends to the person using the measurement instrument . For example, if two researchers use the same instrument (let’s say a measuring tape) and they get different measurements, there’s likely an issue in terms of how one (or both) of them are using the measuring tape. So, when you think about reliability, consider both the instrument and the researcher as part of the equation.

As with validity, there are various types of reliability and various tests that can be used to assess the reliability of an instrument. A popular one that you’ll likely come across for survey instruments is Cronbach’s alpha , which is a statistical measure that quantifies the degree to which items within an instrument (for example, a set of Likert scales) measure the same underlying construct . In other words, Cronbach’s alpha indicates how closely related the items are and whether they consistently capture the same concept . 

Recap: Key Takeaways

Alright, let’s quickly recap to cement your understanding of validity and reliability:

• Validity is concerned with whether an instrument (e.g., a set of Likert scales) is measuring what it’s supposed to measure
• Reliability is concerned with whether that measurement is consistent and stable when measuring the same phenomenon under the same conditions.

In short, validity and reliability are both essential to ensuring that your data collection efforts deliver high-quality, accurate data that help you answer your research questions . So, be sure to always pay careful attention to the validity and reliability of your measurement instruments when collecting and analysing data. As the adage goes, “rubbish in, rubbish out” – make sure that your data inputs are rock-solid.

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5.2 Reliability and Validity of Measurement

Learning objectives.

• Define reliability, including the different types and how they are assessed.
• Define validity, including the different types and how they are assessed.
• Describe the kinds of evidence that would be relevant to assessing the reliability and validity of a particular measure.

Again, measurement involves assigning scores to individuals so that they represent some characteristic of the individuals. But how do researchers know that the scores actually represent the characteristic, especially when it is a construct like intelligence, self-esteem, depression, or working memory capacity? The answer is that they conduct research using the measure to confirm that the scores make sense based on their understanding of the construct being measured. This is an extremely important point. Psychologists do not simply assume that their measures work. Instead, they collect data to demonstrate that they work. If their research does not demonstrate that a measure works, they stop using it.

As an informal example, imagine that you have been dieting for a month. Your clothes seem to be fitting more loosely, and several friends have asked if you have lost weight. If at this point your bathroom scale indicated that you had lost 10 pounds, this would make sense and you would continue to use the scale. But if it indicated that you had gained 10 pounds, you would rightly conclude that it was broken and either fix it or get rid of it. In evaluating a measurement method, psychologists consider two general dimensions: reliability and validity.

Reliability

Reliability refers to the consistency of a measure. Psychologists consider three types of consistency: over time (test-retest reliability), across items (internal consistency), and across different researchers (interrater reliability).

Test-Retest Reliability

When researchers measure a construct that they assume to be consistent across time, then the scores they obtain should also be consistent across time. Test-retest reliability is the extent to which this is actually the case. For example, intelligence is generally thought to be consistent across time. A person who is highly intelligent today will be highly intelligent next week. This means that any good measure of intelligence should produce roughly the same scores for this individual next week as it does today. Clearly, a measure that produces highly inconsistent scores over time cannot be a very good measure of a construct that is supposed to be consistent.

Assessing test-retest reliability requires using the measure on a group of people at one time, using it again on the same group of people at a later time, and then looking at test-retest correlation between the two sets of scores. This is typically done by graphing the data in a scatterplot and computing Pearson’s r . Figure 5.3 “Test-Retest Correlation Between Two Sets of Scores of Several College Students on the Rosenberg Self-Esteem Scale, Given Two Times a Week Apart” shows the correlation between two sets of scores of several college students on the Rosenberg Self-Esteem Scale, given two times a week apart. Pearson’s r for these data is +.95. In general, a test-retest correlation of +.80 or greater is considered to indicate good reliability.

Figure 5.3 Test-Retest Correlation Between Two Sets of Scores of Several College Students on the Rosenberg Self-Esteem Scale, Given Two Times a Week Apart

Again, high test-retest correlations make sense when the construct being measured is assumed to be consistent over time, which is the case for intelligence, self-esteem, and the Big Five personality dimensions. But other constructs are not assumed to be stable over time. The very nature of mood, for example, is that it changes. So a measure of mood that produced a low test-retest correlation over a period of a month would not be a cause for concern.

Internal Consistency

A second kind of reliability is internal consistency , which is the consistency of people’s responses across the items on a multiple-item measure. In general, all the items on such measures are supposed to reflect the same underlying construct, so people’s scores on those items should be correlated with each other. On the Rosenberg Self-Esteem Scale, people who agree that they are a person of worth should tend to agree that that they have a number of good qualities. If people’s responses to the different items are not correlated with each other, then it would no longer make sense to claim that they are all measuring the same underlying construct. This is as true for behavioral and physiological measures as for self-report measures. For example, people might make a series of bets in a simulated game of roulette as a measure of their level of risk seeking. This measure would be internally consistent to the extent that individual participants’ bets were consistently high or low across trials.

Like test-retest reliability, internal consistency can only be assessed by collecting and analyzing data. One approach is to look at a split-half correlation . This involves splitting the items into two sets, such as the first and second halves of the items or the even- and odd-numbered items. Then a score is computed for each set of items, and the relationship between the two sets of scores is examined. For example, Figure 5.4 “Split-Half Correlation Between Several College Students’ Scores on the Even-Numbered Items and Their Scores on the Odd-Numbered Items of the Rosenberg Self-Esteem Scale” shows the split-half correlation between several college students’ scores on the even-numbered items and their scores on the odd-numbered items of the Rosenberg Self-Esteem Scale. Pearson’s r for these data is +.88. A split-half correlation of +.80 or greater is generally considered good internal consistency.

Figure 5.4 Split-Half Correlation Between Several College Students’ Scores on the Even-Numbered Items and Their Scores on the Odd-Numbered Items of the Rosenberg Self-Esteem Scale

Perhaps the most common measure of internal consistency used by researchers in psychology is a statistic called Cronbach’s α (the Greek letter alpha). Conceptually, α is the mean of all possible split-half correlations for a set of items. For example, there are 252 ways to split a set of 10 items into two sets of five. Cronbach’s α would be the mean of the 252 split-half correlations. Note that this is not how α is actually computed, but it is a correct way of interpreting the meaning of this statistic. Again, a value of +.80 or greater is generally taken to indicate good internal consistency.

Interrater Reliability

Many behavioral measures involve significant judgment on the part of an observer or a rater. Interrater reliability is the extent to which different observers are consistent in their judgments. For example, if you were interested in measuring college students’ social skills, you could make video recordings of them as they interacted with another student whom they are meeting for the first time. Then you could have two or more observers watch the videos and rate each student’s level of social skills. To the extent that each participant does in fact have some level of social skills that can be detected by an attentive observer, different observers’ ratings should be highly correlated with each other. If they were not, then those ratings could not be an accurate representation of participants’ social skills. Interrater reliability is often assessed using Cronbach’s α when the judgments are quantitative or an analogous statistic called Cohen’s κ (the Greek letter kappa) when they are categorical.

Validity is the extent to which the scores from a measure represent the variable they are intended to. But how do researchers make this judgment? We have already considered one factor that they take into account—reliability. When a measure has good test-retest reliability and internal consistency, researchers should be more confident that the scores represent what they are supposed to. There has to be more to it, however, because a measure can be extremely reliable but have no validity whatsoever. As an absurd example, imagine someone who believes that people’s index finger length reflects their self-esteem and therefore tries to measure self-esteem by holding a ruler up to people’s index fingers. Although this measure would have extremely good test-retest reliability, it would have absolutely no validity. The fact that one person’s index finger is a centimeter longer than another’s would indicate nothing about which one had higher self-esteem.

Textbook presentations of validity usually divide it into several distinct “types.” But a good way to interpret these types is that they are other kinds of evidence—in addition to reliability—that should be taken into account when judging the validity of a measure. Here we consider four basic kinds: face validity, content validity, criterion validity, and discriminant validity.

Face Validity

Face validity is the extent to which a measurement method appears “on its face” to measure the construct of interest. Most people would expect a self-esteem questionnaire to include items about whether they see themselves as a person of worth and whether they think they have good qualities. So a questionnaire that included these kinds of items would have good face validity. The finger-length method of measuring self-esteem, on the other hand, seems to have nothing to do with self-esteem and therefore has poor face validity. Although face validity can be assessed quantitatively—for example, by having a large sample of people rate a measure in terms of whether it appears to measure what it is intended to—it is usually assessed informally.

Face validity is at best a very weak kind of evidence that a measurement method is measuring what it is supposed to. One reason is that it is based on people’s intuitions about human behavior, which are frequently wrong. It is also the case that many established measures in psychology work quite well despite lacking face validity. The Minnesota Multiphasic Personality Inventory (MMPI) measures many personality characteristics and disorders by having people decide whether each of over 567 different statements applies to them—where many of the statements do not have any obvious relationship to the construct that they measure. Another example is the Implicit Association Test, which measures prejudice in a way that is nonintuitive to most people (see Note 5.31 “How Prejudiced Are You?” ).

How Prejudiced Are You?

The Implicit Association Test (IAT) is used to measure people’s attitudes toward various social groups. The IAT is a behavioral measure designed to reveal negative attitudes that people might not admit to on a self-report measure. It focuses on how quickly people are able to categorize words and images representing two contrasting groups (e.g., gay and straight) along with other positive and negative stimuli (e.g., the words “wonderful” or “nasty”). The IAT has been used in dozens of published research studies, and there is strong evidence for both its reliability and its validity (Nosek, Greenwald, & Banaji, 2006). You can learn more about the IAT—and take several of them for yourself—at the following website: https://implicit.harvard.edu/implicit .

Content Validity

Content validity is the extent to which a measure “covers” the construct of interest. For example, if a researcher conceptually defines test anxiety as involving both sympathetic nervous system activation (leading to nervous feelings) and negative thoughts, then his measure of test anxiety should include items about both nervous feelings and negative thoughts. Or consider that attitudes are usually defined as involving thoughts, feelings, and actions toward something. By this conceptual definition, a person has a positive attitude toward exercise to the extent that he or she thinks positive thoughts about exercising, feels good about exercising, and actually exercises. So to have good content validity, a measure of people’s attitudes toward exercise would have to reflect all three of these aspects. Like face validity, content validity is not usually assessed quantitatively. Instead, it is assessed by carefully checking the measurement method against the conceptual definition of the construct.

Criterion Validity

Criterion validity is the extent to which people’s scores on a measure are correlated with other variables (known as criteria ) that one would expect them to be correlated with. For example, people’s scores on a new measure of test anxiety should be negatively correlated with their performance on an important school exam. If it were found that people’s scores were in fact negatively correlated with their exam performance, then this would be a piece of evidence that these scores really represent people’s test anxiety. But if it were found that people scored equally well on the exam regardless of their test anxiety scores, then this would cast doubt on the validity of the measure.

A criterion can be any variable that one has reason to think should be correlated with the construct being measured, and there will usually be many of them. For example, one would expect test anxiety scores to be negatively correlated with exam performance and course grades and positively correlated with general anxiety and with blood pressure during an exam. Or imagine that a researcher develops a new measure of physical risk taking. People’s scores on this measure should be correlated with their participation in “extreme” activities such as snowboarding and rock climbing, the number of speeding tickets they have received, and even the number of broken bones they have had over the years. Criteria can also include other measures of the same construct. For example, one would expect new measures of test anxiety or physical risk taking to be positively correlated with existing measures of the same constructs. So the use of converging operations is one way to examine criterion validity.

Assessing criterion validity requires collecting data using the measure. Researchers John Cacioppo and Richard Petty did this when they created their self-report Need for Cognition Scale to measure how much people value and engage in thinking (Cacioppo & Petty, 1982). In a series of studies, they showed that college faculty scored higher than assembly-line workers, that people’s scores were positively correlated with their scores on a standardized academic achievement test, and that their scores were negatively correlated with their scores on a measure of dogmatism (which represents a tendency toward obedience). In the years since it was created, the Need for Cognition Scale has been used in literally hundreds of studies and has been shown to be correlated with a wide variety of other variables, including the effectiveness of an advertisement, interest in politics, and juror decisions (Petty, Briñol, Loersch, & McCaslin, 2009).

Discriminant Validity

Discriminant validity is the extent to which scores on a measure are not correlated with measures of variables that are conceptually distinct. For example, self-esteem is a general attitude toward the self that is fairly stable over time. It is not the same as mood, which is how good or bad one happens to be feeling right now. So people’s scores on a new measure of self-esteem should not be very highly correlated with their moods. If the new measure of self-esteem were highly correlated with a measure of mood, it could be argued that the new measure is not really measuring self-esteem; it is measuring mood instead.

When they created the Need for Cognition Scale, Cacioppo and Petty also provided evidence of discriminant validity by showing that people’s scores were not correlated with certain other variables. For example, they found only a weak correlation between people’s need for cognition and a measure of their cognitive style—the extent to which they tend to think analytically by breaking ideas into smaller parts or holistically in terms of “the big picture.” They also found no correlation between people’s need for cognition and measures of their test anxiety and their tendency to respond in socially desirable ways. All these low correlations provide evidence that the measure is reflecting a conceptually distinct construct.

Key Takeaways

• Psychological researchers do not simply assume that their measures work. Instead, they conduct research to show that they work. If they cannot show that they work, they stop using them.
• There are two distinct criteria by which researchers evaluate their measures: reliability and validity. Reliability is consistency across time (test-retest reliability), across items (internal consistency), and across researchers (interrater reliability). Validity is the extent to which the scores actually represent the variable they are intended to.
• Validity is a judgment based on various types of evidence. The relevant evidence includes the measure’s reliability, whether it covers the construct of interest, and whether the scores it produces are correlated with other variables they are expected to be correlated with and not correlated with variables that are conceptually distinct.
• The reliability and validity of a measure is not established by any single study but by the pattern of results across multiple studies. The assessment of reliability and validity is an ongoing process.
• Practice: Ask several friends to complete the Rosenberg Self-Esteem Scale. Then assess its internal consistency by making a scatterplot to show the split-half correlation (even- vs. odd-numbered items). Compute Pearson’s r too if you know how.
• Discussion: Think back to the last college exam you took and think of the exam as a psychological measure. What construct do you think it was intended to measure? Comment on its face and content validity. What data could you collect to assess its reliability, criterion validity, and discriminant validity?
• Practice: Take an Implicit Association Test and then list as many ways to assess its criterion validity as you can think of.

Cacioppo, J. T., & Petty, R. E. (1982). The need for cognition. Journal of Personality and Social Psychology, 42 , 116–131.

Nosek, B. A., Greenwald, A. G., & Banaji, M. R. (2006). The Implicit Association Test at age 7: A methodological and conceptual review. In J. A. Bargh (Ed.), Social psychology and the unconscious: The automaticity of higher mental processes (pp. 265–292). London, England: Psychology Press.

Petty, R. E, Briñol, P., Loersch, C., & McCaslin, M. J. (2009). The need for cognition. In M. R. Leary & R. H. Hoyle (Eds.), Handbook of individual differences in social behavior (pp. 318–329). New York, NY: Guilford Press.

Research Methods in Psychology Copyright © 2016 by University of Minnesota is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

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Statistics By Jim

Making statistics intuitive

Reliability vs Validity: Differences & Examples

By Jim Frost 1 Comment

Reliability and validity are criteria by which researchers assess measurement quality. Measuring a person or item involves assigning scores to represent an attribute. This process creates the data that we analyze. However, to provide meaningful research results, that data must be good. And not all data are good!

For data to be good enough to allow you to draw meaningful conclusions from a research study, they must be reliable and valid. What are the properties of good measurements? In a nutshell, reliability relates to the consistency of measures, and validity addresses whether the measurements are quantifying the correct attribute.

In this post, learn about reliability vs. validity, their relationship, and the various ways to assess them.

Learn more about Experimental Design: Definition, Types, and Examples .

Reliability

Reliability refers to the consistency of the measure. High reliability indicates that the measurement system produces similar results under the same conditions. If you measure the same item or person multiple times, you want to obtain comparable values. They are reproducible.

If you take measurements multiple times and obtain very different values, your data are unreliable. Numbers are meaningless if repeated measures do not produce similar values. What’s the correct value? No one knows! This inconsistency hampers your ability to draw conclusions and understand relationships.

Suppose you have a bathroom scale that displays very inconsistent results from one time to the next. It’s very unreliable. It would be hard to use your scale to determine your correct weight and to know whether you are losing weight.

Inadequate data collection procedures and low-quality or defective data collection tools can produce unreliable data. Additionally, some characteristics are more challenging to measure reliably. For example, the length of an object is concrete. On the other hand, a psychological construct, such as conscientiousness, depression, and self-esteem, can be trickier to measure reliably.

When assessing studies, evaluate data collection methodologies and consider whether any issues undermine their reliability.

Validity refers to whether the measurements reflect what they’re supposed to measure. This concept is a broader issue than reliability. Researchers need to consider whether they’re measuring what they think they’re measuring. Or do the measurements reflect something else? Does the instrument measure what it says it measures? It’s a question that addresses the appropriateness of the data rather than whether measurements are repeatable.

Validity is a smaller concern for tangible measurements like height and weight. You might have a biased bathroom scale if it tends to read too high or too low—but it still measures weight. Validity is a bigger concern in the social sciences, where you can measure elusive concepts such as positive outlook and self-esteem. If you’re assessing the psychological construct of conscientiousness, you need to confirm that the instrument poses questions that appraise this attribute rather than, say, obedience.

Reliability vs Validity

A measurement must be reliable first before it has a chance of being valid. After all, if you don’t obtain consistent measurements for the same object or person under similar conditions, it can’t be valid. If your scale displays a different weight every time you step on it, it’s unreliable, and it is also invalid.

So, having reliable measurements is the first step towards having valid measures. Validity is necessary for reliability, but it is insufficient by itself.

Suppose you have a reliable measurement. You step on your scale a few times in a short period, and it displays very similar weights. It’s reliable. But the weight might be incorrect.

Just because you can measure the same object multiple times and get consistent values, it does not necessarily indicate that the measurements reflect the desired characteristic.

How can you determine whether measurements are both valid and reliable? Assessing reliability vs. validity is the topic for the rest of this post!

How to Assess Reliability

Reliability relates to measurement consistency. To evaluate reliability, analysts assess consistency over time, within the measurement instrument, and between different observers. These types of consistency are also known as—test-retest, internal, and inter-rater reliability. Typically, appraising these forms of reliability involves taking multiple measures of the same person, object, or construct and assessing scatterplots and correlations of the measurements. Reliable measurements have high correlations because the scores are similar.

Test-Retest Reliability

Analysts often assume that measurements should be consistent across a short time. If you measure your height twice over a couple of days, you should obtain roughly the same measurements.

To assess test-retest reliability, the experimenters typically measure a group of participants on two occasions within a few days. Usually, you’ll evaluate the reliability of the repeated measures using scatterplots and correlation coefficients . You expect to see high correlations and tight lines on the scatterplot when the characteristic you measure is consistent over a short period, and you have a reliable measurement system.

This type of reliability establishes the degree to which a test can produce stable, consistent scores across time. However, in practice, measurement instruments are never entirely consistent.

Keep in mind that some characteristics should not be consistent across time. A good example is your mood, which can change from moment to moment. A test-retest assessment of mood is not likely to produce a high correlation even though it might be a useful measurement instrument.

Internal Reliability

This type of reliability assesses consistency across items within a single instrument. Researchers evaluate internal reliability when they’re using instruments such as a survey or personality inventories. In these instruments, multiple items relate to a single construct. Questions that measure the same characteristic should have a high correlation. People who indicate they are risk-takers should also note that they participate in dangerous activities. If items that supposedly measure the same underlying construct have a low correlation, they are not consistent with each other and might not measure the same thing.

Inter-Rater Reliability

This type of reliability assesses consistency across different observers, judges, or evaluators. When various observers produce similar measurements for the same item or person, their scores are highly correlated. Inter-rater reliability is essential when the subjectivity or skill of the evaluator plays a role. For example, assessing the quality of a writing sample involves subjectivity. Researchers can employ rating guidelines to reduce subjectivity. Comparing the scores from different evaluators for the same writing sample helps establish the measure’s reliability. Learn more about inter-rater reliability .

Related post : Interpreting Correlation

Cronbach’s Alpha

Cronbach’s alpha measures the internal consistency, or reliability, of a set of survey items. Use this statistic to help determine whether a collection of items consistently measures the same characteristic. Learn more about Cronbach’s Alpha .

Gage R&R Studies

These studies evaluation a measurement systems reliability and identifies sources of variation that can help you target improvement efforts effectively. Learn more about Gage R&R Studies .

How to Assess Validity

Validity is more difficult to evaluate than reliability. After all, with reliability, you only assess whether the measures are consistent across time, within the instrument, and between observers. On the other hand, evaluating validity involves determining whether the instrument measures the correct characteristic. This process frequently requires examining relationships between these measurements, other data, and theory. Validating a measurement instrument requires you to use a wide range of subject-area knowledge and different types of constructs to determine whether the measurements from your instrument fit in with the bigger picture!

An instrument with high validity produces measurements that correctly fit the larger picture with other constructs. Validity assesses whether the web of empirical relationships aligns with the theoretical relationships.

The measurements must have a positive relationship with other measures of the same construct. Additionally, they need to correlate in the correct direction (positively or negatively) with the theoretically correct constructs. Finally, the measures should have no relationship with unrelated constructs.

If you need more detailed information, read my post that focuses on Measurement Validity . In that post, I cover the various types, how to evaluate them, and provide examples.

Experimental validity relates to experimental designs and methods. To learn about that topic, read my post about Internal and External Validity .

Whew, that’s a lot of information about reliability vs. validity. Using these concepts, you can determine whether a measurement instrument produces good data!

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August 17, 2022 at 3:53 am

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Validity in research: a guide to measuring the right things

Last updated

27 February 2023

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Cathy Heath

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Validity is necessary for all types of studies ranging from market validation of a business or product idea to the effectiveness of medical trials and procedures. So, how can you determine whether your research is valid? This guide can help you understand what validity is, the types of validity in research, and the factors that affect research validity.

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• What is validity?

In the most basic sense, validity is the quality of being based on truth or reason. Valid research strives to eliminate the effects of unrelated information and the circumstances under which evidence is collected. 

Validity in research is the ability to conduct an accurate study with the right tools and conditions to yield acceptable and reliable data that can be reproduced. Researchers rely on carefully calibrated tools for precise measurements. However, collecting accurate information can be more of a challenge.

Studies must be conducted in environments that don't sway the results to achieve and maintain validity. They can be compromised by asking the wrong questions or relying on limited data. 

Why is validity important in research?

Research is used to improve life for humans. Every product and discovery, from innovative medical breakthroughs to advanced new products, depends on accurate research to be dependable. Without it, the results couldn't be trusted, and products would likely fail. Businesses would lose money, and patients couldn't rely on medical treatments. 

While wasting money on a lousy product is a concern, lack of validity paints a much grimmer picture in the medical field or producing automobiles and airplanes, for example. Whether you're launching an exciting new product or conducting scientific research, validity can determine success and failure.

• What is reliability?

Reliability is the ability of a method to yield consistency. If the same result can be consistently achieved by using the same method to measure something, the measurement method is said to be reliable. For example, a thermometer that shows the same temperatures each time in a controlled environment is reliable.

While high reliability is a part of measuring validity, it's only part of the puzzle. If the reliable thermometer hasn't been properly calibrated and reliably measures temperatures two degrees too high, it doesn't provide a valid (accurate) measure of temperature. 

Similarly, if a researcher uses a thermometer to measure weight, the results won't be accurate because it's the wrong tool for the job. 

• How are reliability and validity assessed?

While measuring reliability is a part of measuring validity, there are distinct ways to assess both measurements for accuracy. 

How is reliability measured?

These measures of consistency and stability help assess reliability, including:

Consistency and stability of the same measure when repeated multiple times and conditions

Consistency and stability of the measure across different test subjects

Consistency and stability of results from different parts of a test designed to measure the same thing

How is validity measured?

Since validity refers to how accurately a method measures what it is intended to measure, it can be difficult to assess the accuracy. Validity can be estimated by comparing research results to other relevant data or theories.

The adherence of a measure to existing knowledge of how the concept is measured

The ability to cover all aspects of the concept being measured

The relation of the result in comparison with other valid measures of the same concept

• What are the types of validity in a research design?

Research validity is broadly gathered into two groups: internal and external. Yet, this grouping doesn't clearly define the different types of validity. Research validity can be divided into seven distinct groups.

Face validity : A test that appears valid simply because of the appropriateness or relativity of the testing method, included information, or tools used.

Content validity : The determination that the measure used in research covers the full domain of the content.

Construct validity : The assessment of the suitability of the measurement tool to measure the activity being studied.

Internal validity : The assessment of how your research environment affects measurement results. This is where other factors can’t explain the extent of an observed cause-and-effect response.

External validity : The extent to which the study will be accurate beyond the sample and the level to which it can be generalized in other settings, populations, and measures.

Statistical conclusion validity: The determination of whether a relationship exists between procedures and outcomes (appropriate sampling and measuring procedures along with appropriate statistical tests).

Criterion-related validity : A measurement of the quality of your testing methods against a criterion measure (like a “gold standard” test) that is measured at the same time.

• Examples of validity

Like different types of research and the various ways to measure validity, examples of validity can vary widely. These include:

A questionnaire may be considered valid because each question addresses specific and relevant aspects of the study subject.

In a brand assessment study, researchers can use comparison testing to verify the results of an initial study. For example, the results from a focus group response about brand perception are considered more valid when the results match that of a questionnaire answered by current and potential customers.

A test to measure a class of students' understanding of the English language contains reading, writing, listening, and speaking components to cover the full scope of how language is used.

• Factors that affect research validity

Certain factors can affect research validity in both positive and negative ways. By understanding the factors that improve validity and those that threaten it, you can enhance the validity of your study. These include:

Random selection of participants vs. the selection of participants that are representative of your study criteria

Blinding with interventions the participants are unaware of (like the use of placebos)

Manipulating the experiment by inserting a variable that will change the results

Randomly assigning participants to treatment and control groups to avoid bias

Following specific procedures during the study to avoid unintended effects

Conducting a study in the field instead of a laboratory for more accurate results

Replicating the study with different factors or settings to compare results

Using statistical methods to adjust for inconclusive data

What are the common validity threats in research, and how can their effects be minimized or nullified?

Research validity can be difficult to achieve because of internal and external threats that produce inaccurate results. These factors can jeopardize validity.

History: Events that occur between an early and later measurement

Maturation: The passage of time in a study can include data on actions that would have naturally occurred outside of the settings of the study

Repeated testing: The outcome of repeated tests can change the outcome of followed tests

Selection of subjects: Unconscious bias which can result in the selection of uniform comparison groups

Statistical regression: Choosing subjects based on extremes doesn't yield an accurate outcome for the majority of individuals

Attrition: When the sample group is diminished significantly during the course of the study

Maturation: When subjects mature during the study, and natural maturation is awarded to the effects of the study

While some validity threats can be minimized or wholly nullified, removing all threats from a study is impossible. For example, random selection can remove unconscious bias and statistical regression. 

Researchers can even hope to avoid attrition by using smaller study groups. Yet, smaller study groups could potentially affect the research in other ways. The best practice for researchers to prevent validity threats is through careful environmental planning and t reliable data-gathering methods. 

• How to ensure validity in your research

Researchers should be mindful of the importance of validity in the early planning stages of any study to avoid inaccurate results. Researchers must take the time to consider tools and methods as well as how the testing environment matches closely with the natural environment in which results will be used.

The following steps can be used to ensure validity in research:

Choose appropriate methods of measurement

Use appropriate sampling to choose test subjects

Create an accurate testing environment

How do you maintain validity in research?

Accurate research is usually conducted over a period of time with different test subjects. To maintain validity across an entire study, you must take specific steps to ensure that gathered data has the same levels of accuracy. 

Consistency is crucial for maintaining validity in research. When researchers apply methods consistently and standardize the circumstances under which data is collected, validity can be maintained across the entire study.

Is there a need for validation of the research instrument before its implementation?

An essential part of validity is choosing the right research instrument or method for accurate results. Consider the thermometer that is reliable but still produces inaccurate results. You're unlikely to achieve research validity without activities like calibration, content, and construct validity.

• Understanding research validity for more accurate results

Without validity, research can't provide the accuracy necessary to deliver a useful study. By getting a clear understanding of validity in research, you can take steps to improve your research skills and achieve more accurate results.

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Validity vs. Reliability in Research: What's the Difference?

Introduction

What is the difference between reliability and validity in a study, what is an example of reliability and validity, how to ensure validity and reliability in your research, critiques of reliability and validity.

In research, validity and reliability are crucial for producing robust findings. They provide a foundation that assures scholars, practitioners, and readers alike that the research's insights are both accurate and consistent. However, the nuanced nature of qualitative data often blurs the lines between these concepts, making it imperative for researchers to discern their distinct roles.

This article seeks to illuminate the intricacies of reliability and validity, highlighting their significance and distinguishing their unique attributes. By understanding these critical facets, qualitative researchers can ensure their work not only resonates with authenticity but also trustworthiness.

In the domain of research, whether qualitative or quantitative , two concepts often arise when discussing the quality and rigor of a study: reliability and validity . These two terms, while interconnected, have distinct meanings that hold significant weight in the world of research.

Reliability, at its core, speaks to the consistency of a study. If a study or test measures the same concept repeatedly and yields the same results, it demonstrates a high degree of reliability. A common method for assessing reliability is through internal consistency reliability, which checks if multiple items that measure the same concept produce similar scores.

Another method often used is inter-rater reliability , which gauges the consistency of scores given by different raters. This approach is especially amenable to qualitative research , and it can help researchers assess the clarity of their code system and the consistency of their codings . For a study to be more dependable, it's imperative to ensure a sufficient measurement of reliability is achieved.

On the other hand, validity is concerned with accuracy. It looks at whether a study truly measures what it claims to. Within the realm of validity, several types exist. Construct validity, for instance, verifies that a study measures the intended abstract concept or underlying construct. If a research aims to measure self-esteem and accurately captures this abstract trait, it demonstrates strong construct validity.

Content validity ensures that a test or study comprehensively represents the entire domain of the concept it seeks to measure. For instance, if a test aims to assess mathematical ability, it should cover arithmetic, algebra, geometry, and more to showcase strong content validity.

Criterion validity is another form of validity that ensures that the scores from a test correlate well with a measure from a related outcome. A subset of this is predictive validity, which checks if the test can predict future outcomes. For instance, if an aptitude test can predict future job performance, it can be said to have high predictive validity.

The distinction between reliability and validity becomes clear when one considers the nature of their focus. While reliability is concerned with consistency and reproducibility, validity zeroes in on accuracy and truthfulness.

A research tool can be reliable without being valid. For instance, faulty instrument measures might consistently give bad readings (reliable but not valid). Conversely, in discussions about test reliability, the same test measure administered multiple times could sometimes hit the mark and at other times miss it entirely, producing different test scores each time. This would make it valid in some instances but not reliable.

For a study to be robust, it must achieve both reliability and validity. Reliability ensures the study's findings are reproducible while validity confirms that it accurately represents the phenomena it claims to. Ensuring both in a study means the results are both dependable and accurate, forming a cornerstone for high-quality research.

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Understanding the nuances of reliability and validity becomes clearer when contextualized within a real-world research setting. Imagine a qualitative study where a researcher aims to explore the experiences of teachers in urban schools concerning classroom management. The primary method of data collection is semi-structured interviews .

To ensure the reliability of this qualitative study, the researcher crafts a consistent list of open-ended questions for the interview. This ensures that, while each conversation might meander based on the individual’s experiences, there remains a core set of topics related to classroom management that every participant addresses.

The essence of reliability in this context isn't necessarily about garnering identical responses but rather about achieving a consistent approach to data collection and subsequent interpretation . As part of this commitment to reliability, two researchers might independently transcribe and analyze a subset of these interviews. If they identify similar themes and patterns in their independent analyses, it suggests a consistent interpretation of the data, showcasing inter-rater reliability .

Validity , on the other hand, is anchored in ensuring that the research genuinely captures and represents the lived experiences and sentiments of teachers concerning classroom management. To establish content validity, the list of interview questions is thoroughly reviewed by a panel of educational experts. Their feedback ensures that the questions encompass the breadth of issues and concerns related to classroom management in urban school settings.

As the interviews are conducted, the researcher pays close attention to the depth and authenticity of responses. After the interviews, member checking could be employed, where participants review the researcher's interpretation of their responses to ensure that their experiences and perspectives have been accurately captured. This strategy helps in affirming the study's construct validity, ensuring that the abstract concept of "experiences with classroom management" has been truthfully and adequately represented.

In this example, we can see that while the interview study is rooted in qualitative methods and subjective experiences, the principles of reliability and validity can still meaningfully inform the research process. They serve as guides to ensure the research's findings are both dependable and genuinely reflective of the participants' experiences.

Ensuring validity and reliability in research, irrespective of its qualitative or quantitative nature, is pivotal to producing results that are both trustworthy and robust. Here's how you can integrate these concepts into your study to ensure its rigor:

Reliability is about consistency. One of the most straightforward ways to gauge it in quantitative research is using test-retest reliability. It involves administering the same test to the same group of participants on two separate occasions and then comparing the results.

A high degree of similarity between the two sets of results indicates good reliability. This can often be measured using a correlation coefficient, where a value closer to 1 indicates a strong positive consistency between the two test iterations.

Validity, on the other hand, ensures that the research genuinely measures what it intends to. There are various forms of validity to consider. Convergent validity ensures that two measures of the same construct or those that should theoretically be related, are indeed correlated. For example, two different measures assessing self-esteem should show similar results for the same group, highlighting that they are measuring the same underlying construct.

Face validity is the most basic form of validity and is gauged by the sheer appearance of the measurement tool. If, at face value, a test seems like it measures what it claims to, it has face validity. This is often the first step and is usually followed by more rigorous forms of validity testing.

Criterion-related validity, a subtype of the previously discussed criterion validity, evaluates how well the outcomes of a particular test or measurement correlate with another related measure. For example, if a new tool is developed to measure reading comprehension, its results can be compared with those of an established reading comprehension test to assess its criterion-related validity. If the results show a strong correlation, it's a sign that the new tool is valid.

Ensuring both validity and reliability requires deliberate planning, meticulous testing, and constant reflection on the study's methods and results. This might involve using established scales or measures with proven validity and reliability, conducting pilot studies to refine measurement tools, and always staying cognizant of the fact that these two concepts are important considerations for research robustness.

While reliability and validity are foundational concepts in many traditional research paradigms, they have not escaped scrutiny, especially from critical and poststructuralist perspectives. These critiques often arise from the fundamental philosophical differences in how knowledge, truth, and reality are perceived and constructed.

From a poststructuralist viewpoint, the very pursuit of a singular "truth" or an objective reality is questionable. In such a perspective, multiple truths exist, each shaped by its own socio-cultural, historical, and individual contexts.

Reliability, with its emphasis on consistent replication, might then seem at odds with this understanding. If truths are multiple and shifting, how can consistency across repeated measures or observations be a valid measure of anything other than the research instrument's stability?

Validity, too, faces critique. In seeking to ensure that a study measures what it purports to measure, there's an implicit assumption of an observable, knowable reality. Poststructuralist critiques question this foundation, arguing that reality is too fluid, multifaceted, and influenced by power dynamics to be pinned down by any singular measurement or representation.

Moreover, the very act of determining "validity" often requires an external benchmark or "gold standard." This brings up the issue of who determines this standard and the power dynamics and potential biases inherent in such decisions.

Another point of contention is the way these concepts can inadvertently prioritize certain forms of knowledge over others. For instance, privileging research that meets stringent reliability and validity criteria might marginalize more exploratory, interpretive, or indigenous research methods. These methods, while offering deep insights, might not align neatly with traditional understandings of reliability and validity, potentially relegating them to the periphery of "accepted" knowledge production.

To be sure, reliability and validity serve as guiding principles in many research approaches. However, it's essential to recognize their limitations and the critiques posed by alternative epistemologies. Engaging with these critiques doesn't diminish the value of reliability and validity but rather enriches our understanding of the multifaceted nature of knowledge and the complexities of its pursuit.

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Home » Reliability – Types, Examples and Guide

Reliability – Types, Examples and Guide

Table of Contents

Reliability

Definition:

Reliability refers to the consistency, dependability, and trustworthiness of a system, process, or measurement to perform its intended function or produce consistent results over time. It is a desirable characteristic in various domains, including engineering, manufacturing, software development, and data analysis.

Reliability In Engineering

In engineering and manufacturing, reliability refers to the ability of a product, equipment, or system to function without failure or breakdown under normal operating conditions for a specified period. A reliable system consistently performs its intended functions, meets performance requirements, and withstands various environmental factors, stress, or wear and tear.

Reliability In Software Development

In software development, reliability relates to the stability and consistency of software applications or systems. A reliable software program operates consistently without crashing, produces accurate results, and handles errors or exceptions gracefully. Reliability is often measured by metrics such as mean time between failures (MTBF) and mean time to repair (MTTR).

Reliability In Data Analysis and Statistics

In data analysis and statistics, reliability refers to the consistency and repeatability of measurements or assessments. For example, if a measurement instrument consistently produces similar results when measuring the same quantity or if multiple raters consistently agree on the same assessment, it is considered reliable. Reliability is often assessed using statistical measures such as test-retest reliability, inter-rater reliability, or internal consistency.

Research Reliability

Research reliability refers to the consistency, stability, and repeatability of research findings . It indicates the extent to which a research study produces consistent and dependable results when conducted under similar conditions. In other words, research reliability assesses whether the same results would be obtained if the study were replicated with the same methodology, sample, and context.

What Affects Reliability in Research

Several factors can affect the reliability of research measurements and assessments. Here are some common factors that can impact reliability:

Measurement Error

Measurement error refers to the variability or inconsistency in the measurements that is not due to the construct being measured. It can arise from various sources, such as the limitations of the measurement instrument, environmental factors, or the characteristics of the participants. Measurement error reduces the reliability of the measure by introducing random variability into the data.

Rater/Observer Bias

In studies involving subjective assessments or ratings, the biases or subjective judgments of the raters or observers can affect reliability. If different raters interpret and evaluate the same phenomenon differently, it can lead to inconsistencies in the ratings, resulting in lower inter-rater reliability.

Participant Factors

Characteristics or factors related to the participants themselves can influence reliability. For example, factors such as fatigue, motivation, attention, or mood can introduce variability in responses, affecting the reliability of self-report measures or performance assessments.

Instrumentation

The quality and characteristics of the measurement instrument can impact reliability. If the instrument lacks clarity, has ambiguous items or instructions, or is prone to measurement errors, it can decrease the reliability of the measure. Poorly designed or unreliable instruments can introduce measurement error and decrease the consistency of the measurements.

Sample Size

Sample size can affect reliability, especially in studies where the reliability coefficient is based on correlations or variability within the sample. A larger sample size generally provides more stable estimates of reliability, while smaller samples can yield less precise estimates.

Time Interval

The time interval between test administrations can impact test-retest reliability. If the time interval is too short, participants may recall their previous responses and answer in a similar manner, artificially inflating the reliability coefficient. On the other hand, if the time interval is too long, true changes in the construct being measured may occur, leading to lower test-retest reliability.

Content Sampling

The specific items or questions included in a measure can affect reliability. If the measure does not adequately sample the full range of the construct being measured or if the items are too similar or redundant, it can result in lower internal consistency reliability.

Scoring and Data Handling

Errors in scoring, data entry, or data handling can introduce variability and impact reliability. Inaccurate or inconsistent scoring procedures, data entry mistakes, or mishandling of missing data can affect the reliability of the measurements.

Context and Environment

The context and environment in which measurements are obtained can influence reliability. Factors such as noise, distractions, lighting conditions, or the presence of others can introduce variability and affect the consistency of the measurements.

Types of Reliability

There are several types of reliability that are commonly discussed in research and measurement contexts. Here are some of the main types of reliability:

Test-Retest Reliability

This type of reliability assesses the consistency of a measure over time. It involves administering the same test or measure to the same group of individuals on two separate occasions and then comparing the results. If the scores are similar or highly correlated across the two testing points, it indicates good test-retest reliability.

Inter-Rater Reliability

Inter-rater reliability examines the degree of agreement or consistency between different raters or observers who are assessing the same phenomenon. It is commonly used in subjective evaluations or assessments where judgments are made by multiple individuals. High inter-rater reliability suggests that different observers are likely to reach the same conclusions or make consistent assessments.

Internal Consistency Reliability

Internal consistency reliability assesses the extent to which the items or questions within a measure are consistent with each other. It is commonly measured using techniques such as Cronbach’s alpha. High internal consistency reliability indicates that the items within a measure are measuring the same construct or concept consistently.

Parallel Forms Reliability

Parallel forms reliability assesses the consistency of different versions or forms of a test that are intended to measure the same construct. Two equivalent versions of a test are administered to the same group of individuals, and the scores are compared to determine the level of agreement between the forms.

Split-Half Reliability

Split-half reliability involves splitting a measure into two halves and examining the consistency between the two halves. It can be done by dividing the items into odd-even pairs or by randomly splitting the items. The scores from the two halves are then compared to assess the degree of consistency.

Alternate Forms Reliability

Alternate forms reliability is similar to parallel forms reliability, but it involves administering two different versions of a test to the same group of individuals. The two forms should be equivalent and measure the same construct. The scores from the two forms are then compared to assess the level of agreement.

Applications of Reliability

Reliability has several important applications across various fields and disciplines. Here are some common applications of reliability:

Psychological and Educational Testing

Reliability is crucial in psychological and educational testing to ensure that the scores obtained from assessments are consistent and dependable. It helps to determine the accuracy and stability of measures such as intelligence tests, personality assessments, academic exams, and aptitude tests.

Market Research

In market research, reliability is important for ensuring consistent and dependable data collection. Surveys, questionnaires, and other data collection instruments need to have high reliability to obtain accurate and consistent responses from participants. Reliability analysis helps researchers identify and address any issues that may affect the consistency of the data.

Health and Medical Research

Reliability is essential in health and medical research to ensure that measurements and assessments used in studies are consistent and trustworthy. This includes the reliability of diagnostic tests, patient-reported outcome measures, observational measures, and psychometric scales. High reliability is crucial for making valid inferences and drawing reliable conclusions from research findings.

Quality Control and Manufacturing

Reliability analysis is widely used in industries such as manufacturing and quality control to assess the reliability of products and processes. It helps to identify and address sources of variation and inconsistency, ensuring that products meet the required standards and specifications consistently.

Social Science Research

Reliability plays a vital role in social science research, including fields such as sociology, anthropology, and political science. It is used to assess the consistency of measurement tools, such as surveys or observational protocols, to ensure that the data collected is reliable and can be trusted for analysis and interpretation.

Performance Evaluation

Reliability is important in performance evaluation systems used in organizations and workplaces. Whether it’s assessing employee performance, evaluating the reliability of scoring rubrics, or measuring the consistency of ratings by supervisors, reliability analysis helps ensure fairness and consistency in the evaluation process.

Psychometrics and Scale Development

Reliability analysis is a fundamental step in psychometrics, which involves developing and validating measurement scales. Researchers assess the reliability of items and subscales to ensure that the scale measures the intended construct consistently and accurately.

Examples of Reliability

Here are some examples of reliability in different contexts:

Test-Retest Reliability Example: A researcher administers a personality questionnaire to a group of participants and then administers the same questionnaire to the same participants after a certain period, such as two weeks. The scores obtained from the two administrations are highly correlated, indicating good test-retest reliability.

Inter-Rater Reliability Example: Multiple teachers assess the essays of a group of students using a standardized grading rubric. The ratings assigned by the teachers show a high level of agreement or correlation, indicating good inter-rater reliability.

Internal Consistency Reliability Example: A researcher develops a questionnaire to measure job satisfaction. The researcher administers the questionnaire to a group of employees and calculates Cronbach’s alpha to assess internal consistency. The calculated value of Cronbach’s alpha is high (e.g., above 0.8), indicating good internal consistency reliability.

Parallel Forms Reliability Example: Two versions of a mathematics exam are created, which are designed to measure the same mathematical skills. Both versions of the exam are administered to the same group of students, and the scores from the two versions are highly correlated, indicating good parallel forms reliability.

Split-Half Reliability Example: A researcher develops a survey to measure self-esteem. The survey consists of 20 items, and the researcher randomly divides the items into two halves. The scores obtained from each half of the survey show a high level of agreement or correlation, indicating good split-half reliability.

Alternate Forms Reliability Example: A researcher develops two versions of a language proficiency test, which are designed to measure the same language skills. Both versions of the test are administered to the same group of participants, and the scores from the two versions are highly correlated, indicating good alternate forms reliability.

Where to Write About Reliability in A Thesis

When writing about reliability in a thesis, there are several sections where you can address this topic. Here are some common sections in a thesis where you can discuss reliability:

Introduction :

In the introduction section of your thesis, you can provide an overview of the study and briefly introduce the concept of reliability. Explain why reliability is important in your research field and how it relates to your study objectives.

Theoretical Framework:

If your thesis includes a theoretical framework or a literature review, this is a suitable section to discuss reliability. Provide an overview of the relevant theories, models, or concepts related to reliability in your field. Discuss how other researchers have measured and assessed reliability in similar studies.

Methodology:

The methodology section is crucial for addressing reliability. Describe the research design, data collection methods, and measurement instruments used in your study. Explain how you ensured the reliability of your measurements or data collection procedures. This may involve discussing pilot studies, inter-rater reliability, test-retest reliability, or other techniques used to assess and improve reliability.

Data Analysis:

In the data analysis section, you can discuss the statistical techniques employed to assess the reliability of your data. This might include measures such as Cronbach’s alpha, Cohen’s kappa, or intraclass correlation coefficients (ICC), depending on the nature of your data and research design. Present the results of reliability analyses and interpret their implications for your study.

Discussion:

In the discussion section, analyze and interpret the reliability results in relation to your research findings and objectives. Discuss any limitations or challenges encountered in establishing or maintaining reliability in your study. Consider the implications of reliability for the validity and generalizability of your results.

Conclusion:

In the conclusion section, summarize the main points discussed in your thesis regarding reliability. Emphasize the importance of reliability in research and highlight any recommendations or suggestions for future studies to enhance reliability.

Importance of Reliability

Reliability is of utmost importance in research, measurement, and various practical applications. Here are some key reasons why reliability is important:

• Consistency : Reliability ensures consistency in measurements and assessments. Consistent results indicate that the measure or instrument is stable and produces similar outcomes when applied repeatedly. This consistency allows researchers and practitioners to have confidence in the reliability of the data collected and the conclusions drawn from it.
• Accuracy : Reliability is closely linked to accuracy. A reliable measure produces results that are close to the true value or state of the phenomenon being measured. When a measure is unreliable, it introduces error and uncertainty into the data, which can lead to incorrect interpretations and flawed decision-making.
• Trustworthiness : Reliability enhances the trustworthiness of measurements and assessments. When a measure is reliable, it indicates that it is dependable and can be trusted to provide consistent and accurate results. This is particularly important in fields where decisions and actions are based on the data collected, such as education, healthcare, and market research.
• Comparability : Reliability enables meaningful comparisons between different groups, individuals, or time points. When measures are reliable, differences or changes observed can be attributed to true differences in the underlying construct, rather than measurement error. This allows for valid comparisons and evaluations, both within a study and across different studies.
• Validity : Reliability is a prerequisite for validity. Validity refers to the extent to which a measure or assessment accurately captures the construct it is intended to measure. If a measure is unreliable, it cannot be valid, as it does not consistently reflect the construct of interest. Establishing reliability is an important step in establishing the validity of a measure.
• Decision-making : Reliability is crucial for making informed decisions based on data. Whether it’s evaluating employee performance, diagnosing medical conditions, or conducting research studies, reliable measurements and assessments provide a solid foundation for decision-making processes. They help to reduce uncertainty and increase confidence in the conclusions drawn from the data.
• Quality Assurance : Reliability is essential for maintaining quality assurance in various fields. It allows organizations to assess and monitor the consistency and dependability of their processes, products, and services. By ensuring reliability, organizations can identify areas of improvement, address sources of variation, and deliver consistent and high-quality outcomes.

Limitations of Reliability

Here are some limitations of reliability:

• Limited to consistency: Reliability primarily focuses on the consistency of measurements and findings. However, it does not guarantee the accuracy or validity of the measurements. A measurement can be consistent but still systematically biased or flawed, leading to inaccurate results. Reliability alone cannot address validity concerns.
• Context-dependent: Reliability can be influenced by the specific context, conditions, or population under study. A measurement or instrument that demonstrates high reliability in one context may not necessarily exhibit the same level of reliability in a different context. Researchers need to consider the specific characteristics and limitations of their study context when interpreting reliability.
• Inadequate for complex constructs: Reliability is often based on the assumption of unidimensionality, which means that a measurement instrument is designed to capture a single construct. However, many real-world phenomena are complex and multidimensional, making it challenging to assess reliability accurately. Reliability measures may not adequately capture the full complexity of such constructs.
• Susceptible to systematic errors: Reliability focuses on minimizing random errors, but it may not detect or address systematic errors or biases in measurements. Systematic errors can arise from flaws in the measurement instrument, data collection procedures, or sample selection. Reliability assessments may not fully capture or address these systematic errors, leading to biased or inaccurate results.
• Relies on assumptions: Reliability assessments often rely on certain assumptions, such as the assumption of measurement invariance or the assumption of stable conditions over time. These assumptions may not always hold true in real-world research settings, particularly when studying dynamic or evolving phenomena. Failure to meet these assumptions can compromise the reliability of the research.
• Limited to quantitative measures: Reliability is typically applied to quantitative measures and instruments, which can be problematic when studying qualitative or subjective phenomena. Reliability measures may not fully capture the richness and complexity of qualitative data, limiting their applicability in certain research domains.

Also see Reliability Vs Validity

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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A Primer on the Validity of Assessment Instruments

1. what is reliability 1.

Reliability refers to whether an assessment instrument gives the same results each time it is used in the same setting with the same type of subjects. Reliability essentially means consistent or dependable results. Reliability is a part of the assessment of validity.

2. What is validity? 1

Validity in research refers to how accurately a study answers the study question or the strength of the study conclusions. For outcome measures such as surveys or tests, validity refers to the accuracy of measurement. Here validity refers to how well the assessment tool actually measures the underlying outcome of interest. Validity is not a property of the tool itself, but rather of the interpretation or specific purpose of the assessment tool with particular settings and learners.

Assessment instruments must be both reliable and valid for study results to be credible. Thus, reliability and validity must be examined and reported, or references cited, for each assessment instrument used to measure study outcomes. Examples of assessments include resident feedback survey, course evaluation, written test, clinical simulation observer ratings, needs assessment survey, and teacher evaluation. Using an instrument with high reliability is not sufficient; other measures of validity are needed to establish the credibility of your study.

3. How is reliability measured? 2 – 4

Reliability can be estimated in several ways; the method will depend upon the type of assessment instrument. Sometimes reliability is referred to as internal validity or internal structure of the assessment tool.

For internal consistency 2 to 3 questions or items are created that measure the same concept, and the difference among the answers is calculated. That is, the correlation among the answers is measured.

Cronbach alpha is a test of internal consistency and frequently used to calculate the correlation values among the answers on your assessment tool. 5 Cronbach alpha calculates correlation among all the variables, in every combination; a high reliability estimate should be as close to 1 as possible.

For test/retest the test should give the same results each time, assuming there are no interval changes in what you are measuring, and they are often measured as correlation, with Pearson r.

Test/retest is a more conservative estimate of reliability than Cronbach alpha, but it takes at least 2 administrations of the tool, whereas Cronbach alpha can be calculated after a single administration. To perform a test/retest, you must be able to minimize or eliminate any change (ie, learning) in the condition you are measuring, between the 2 measurement times. Administer the assessment instrument at 2 separate times for each subject and calculate the correlation between the 2 different measurements.

Interrater reliability is used to study the effect of different raters or observers using the same tool and is generally estimated by percent agreement, kappa (for binary outcomes), or Kendall tau.

Another method uses analysis of variance (ANOVA) to generate a generalizability coefficient, to quantify how much measurement error can be attributed to each potential factor, such as different test items, subjects, raters, dates of administration, and so forth. This model looks at the overall reliability of the results. 6

5. How is the validity of an assessment instrument determined? 4 – 7 , 8

Validity of assessment instruments requires several sources of evidence to build the case that the instrument measures what it is supposed to measure. , 9,10 Determining validity can be viewed as constructing an evidence-based argument regarding how well a tool measures what it is supposed to do. Evidence can be assembled to support, or not support, a specific use of the assessment tool. Evidence can be found in content, response process, relationships to other variables, and consequences.

Content includes a description of the steps used to develop the instrument. Provide information such as who created the instrument (national experts would confer greater validity than local experts, who in turn would have more validity than nonexperts) and other steps that support the instrument has the appropriate content.

Response process includes information about whether the actions or thoughts of the subjects actually match the test and also information regarding training for the raters/observers, instructions for the test-takers, instructions for scoring, and clarity of these materials.

Relationship to other variables includes correlation of the new assessment instrument results with other performance outcomes that would likely be the same. If there is a previously accepted “gold standard” of measurement, correlate the instrument results to the subject's performance on the “gold standard.” In many cases, no “gold standard” exists and comparison is made to other assessments that appear reasonable (eg, in-training examinations, objective structured clinical examinations, rotation “grades,” similar surveys).

Consequences means that if there are pass/fail or cut-off performance scores, those grouped in each category tend to perform the same in other settings. Also, if lower performers receive additional training and their scores improve, this would add to the validity of the instrument.

Different types of instruments need an emphasis on different sources of validity evidence. 7 For example, for observer ratings of resident performance, interrater agreement may be key, whereas for a survey measuring resident stress, relationship to other variables may be more important. For a multiple choice examination, content and consequences may be essential sources of validity evidence. For high-stakes assessments (eg, board examinations), substantial evidence to support the case for validity will be required. 9

There are also other types of validity evidence, which are not discussed here.

6. How can researchers enhance the validity of their assessment instruments?

First, do a literature search and use previously developed outcome measures. If the instrument must be modified for use with your subjects or setting, modify and describe how, in a transparent way. Include sufficient detail to allow readers to understand the potential limitations of this approach.

If no assessment instruments are available, use content experts to create your own and pilot the instrument prior to using it in your study. Test reliability and include as many sources of validity evidence as are possible in your paper. Discuss the limitations of this approach openly.

7. What are the expectations of JGME editors regarding assessment instruments used in graduate medical education research?

JGME editors expect that discussions of the validity of your assessment tools will be explicitly mentioned in your manuscript, in the methods section. If you are using a previously studied tool in the same setting, with the same subjects, and for the same purpose, citing the reference(s) is sufficient. Additional discussion about your adaptation is needed if you (1) have modified previously studied instruments; (2) are using the instrument for different settings, subjects, or purposes; or (3) are using different interpretation or cut-off points. Discuss whether the changes are likely to affect the reliability or validity of the instrument.

Researchers who create novel assessment instruments need to state the development process, reliability measures, pilot results, and any other information that may lend credibility to the use of homegrown instruments. Transparency enhances credibility.

In general, little information can be gleaned from single-site studies using untested assessment instruments; these studies are unlikely to be accepted for publication.

8. What are useful resources for reliability and validity of assessment instruments?

The references for this editorial are a good starting point.

Gail M. Sullivan, MD, MPH, is Editor-in-Chief, Journal of Graduate Medical Education .

Understanding Reliability and Validity

These related research issues ask us to consider whether we are studying what we think we are studying and whether the measures we use are consistent.

Reliability

Reliability is the extent to which an experiment, test, or any measuring procedure yields the same result on repeated trials. Without the agreement of independent observers able to replicate research procedures, or the ability to use research tools and procedures that yield consistent measurements, researchers would be unable to satisfactorily draw conclusions, formulate theories, or make claims about the generalizability of their research. In addition to its important role in research, reliability is critical for many parts of our lives, including manufacturing, medicine, and sports.

Reliability is such an important concept that it has been defined in terms of its application to a wide range of activities. For researchers, four key types of reliability are:

Equivalency Reliability

Equivalency reliability is the extent to which two items measure identical concepts at an identical level of difficulty. Equivalency reliability is determined by relating two sets of test scores to one another to highlight the degree of relationship or association. In quantitative studies and particularly in experimental studies, a correlation coefficient, statistically referred to as r , is used to show the strength of the correlation between a dependent variable (the subject under study), and one or more independent variables , which are manipulated to determine effects on the dependent variable. An important consideration is that equivalency reliability is concerned with correlational, not causal, relationships.

For example, a researcher studying university English students happened to notice that when some students were studying for finals, their holiday shopping began. Intrigued by this, the researcher attempted to observe how often, or to what degree, this these two behaviors co-occurred throughout the academic year. The researcher used the results of the observations to assess the correlation between studying throughout the academic year and shopping for gifts. The researcher concluded there was poor equivalency reliability between the two actions. In other words, studying was not a reliable predictor of shopping for gifts.

Stability Reliability

Stability reliability (sometimes called test, re-test reliability) is the agreement of measuring instruments over time. To determine stability, a measure or test is repeated on the same subjects at a future date. Results are compared and correlated with the initial test to give a measure of stability.

An example of stability reliability would be the method of maintaining weights used by the U.S. Bureau of Standards. Platinum objects of fixed weight (one kilogram, one pound, etc...) are kept locked away. Once a year they are taken out and weighed, allowing scales to be reset so they are "weighing" accurately. Keeping track of how much the scales are off from year to year establishes a stability reliability for these instruments. In this instance, the platinum weights themselves are assumed to have a perfectly fixed stability reliability.

Internal Consistency

Internal consistency is the extent to which tests or procedures assess the same characteristic, skill or quality. It is a measure of the precision between the observers or of the measuring instruments used in a study. This type of reliability often helps researchers interpret data and predict the value of scores and the limits of the relationship among variables.

For example, a researcher designs a questionnaire to find out about college students' dissatisfaction with a particular textbook. Analyzing the internal consistency of the survey items dealing with dissatisfaction will reveal the extent to which items on the questionnaire focus on the notion of dissatisfaction.

Interrater Reliability

Interrater reliability is the extent to which two or more individuals (coders or raters) agree. Interrater reliability addresses the consistency of the implementation of a rating system.

A test of interrater reliability would be the following scenario: Two or more researchers are observing a high school classroom. The class is discussing a movie that they have just viewed as a group. The researchers have a sliding rating scale (1 being most positive, 5 being most negative) with which they are rating the student's oral responses. Interrater reliability assesses the consistency of how the rating system is implemented. For example, if one researcher gives a "1" to a student response, while another researcher gives a "5," obviously the interrater reliability would be inconsistent. Interrater reliability is dependent upon the ability of two or more individuals to be consistent. Training, education and monitoring skills can enhance interrater reliability.

Related Information: Reliability Example

An example of the importance of reliability is the use of measuring devices in Olympic track and field events. For the vast majority of people, ordinary measuring rulers and their degree of accuracy are reliable enough. However, for an Olympic event, such as the discus throw, the slightest variation in a measuring device -- whether it is a tape, clock, or other device -- could mean the difference between the gold and silver medals. Additionally, it could mean the difference between a new world record and outright failure to qualify for an event. Olympic measuring devices, then, must be reliable from one throw or race to another and from one competition to another. They must also be reliable when used in different parts of the world, as temperature, air pressure, humidity, interpretation, or other variables might affect their readings.

Validity refers to the degree to which a study accurately reflects or assesses the specific concept that the researcher is attempting to measure. While reliability is concerned with the accuracy of the actual measuring instrument or procedure, validity is concerned with the study's success at measuring what the researchers set out to measure.

Researchers should be concerned with both external and internal validity. External validity refers to the extent to which the results of a study are generalizable or transferable. (Most discussions of external validity focus solely on generalizability; see Campbell and Stanley, 1966. We include a reference here to transferability because many qualitative research studies are not designed to be generalized.)

Internal validity refers to (1) the rigor with which the study was conducted (e.g., the study's design, the care taken to conduct measurements, and decisions concerning what was and wasn't measured) and (2) the extent to which the designers of a study have taken into account alternative explanations for any causal relationships they explore (Huitt, 1998). In studies that do not explore causal relationships, only the first of these definitions should be considered when assessing internal validity.

Scholars discuss several types of internal validity. For brief discussions of several types of internal validity, click on the items below:

Face Validity

Face validity is concerned with how a measure or procedure appears. Does it seem like a reasonable way to gain the information the researchers are attempting to obtain? Does it seem well designed? Does it seem as though it will work reliably? Unlike content validity, face validity does not depend on established theories for support (Fink, 1995).

Criterion Related Validity

Criterion related validity, also referred to as instrumental validity, is used to demonstrate the accuracy of a measure or procedure by comparing it with another measure or procedure which has been demonstrated to be valid.

For example, imagine a hands-on driving test has been shown to be an accurate test of driving skills. By comparing the scores on the written driving test with the scores from the hands-on driving test, the written test can be validated by using a criterion related strategy in which the hands-on driving test is compared to the written test.

Construct Validity

Construct validity seeks agreement between a theoretical concept and a specific measuring device or procedure. For example, a researcher inventing a new IQ test might spend a great deal of time attempting to "define" intelligence in order to reach an acceptable level of construct validity.

Construct validity can be broken down into two sub-categories: Convergent validity and discriminate validity. Convergent validity is the actual general agreement among ratings, gathered independently of one another, where measures should be theoretically related. Discriminate validity is the lack of a relationship among measures which theoretically should not be related.

To understand whether a piece of research has construct validity, three steps should be followed. First, the theoretical relationships must be specified. Second, the empirical relationships between the measures of the concepts must be examined. Third, the empirical evidence must be interpreted in terms of how it clarifies the construct validity of the particular measure being tested (Carmines & Zeller, p. 23).

Content Validity

Content Validity is based on the extent to which a measurement reflects the specific intended domain of content (Carmines & Zeller, 1991, p.20).

Content validity is illustrated using the following examples: Researchers aim to study mathematical learning and create a survey to test for mathematical skill. If these researchers only tested for multiplication and then drew conclusions from that survey, their study would not show content validity because it excludes other mathematical functions. Although the establishment of content validity for placement-type exams seems relatively straight-forward, the process becomes more complex as it moves into the more abstract domain of socio-cultural studies. For example, a researcher needing to measure an attitude like self-esteem must decide what constitutes a relevant domain of content for that attitude. For socio-cultural studies, content validity forces the researchers to define the very domains they are attempting to study.

Related Information: Validity Example

Many recreational activities of high school students involve driving cars. A researcher, wanting to measure whether recreational activities have a negative effect on grade point average in high school students, might conduct a survey asking how many students drive to school and then attempt to find a correlation between these two factors. Because many students might use their cars for purposes other than or in addition to recreation (e.g., driving to work after school, driving to school rather than walking or taking a bus), this research study might prove invalid. Even if a strong correlation was found between driving and grade point average, driving to school in and of itself would seem to be an invalid measure of recreational activity.

The challenges of achieving reliability and validity are among the most difficult faced by researchers. In this section, we offer commentaries on these challenges.

Difficulties of Achieving Reliability

It is important to understand some of the problems concerning reliability which might arise. It would be ideal to reliably measure, every time, exactly those things which we intend to measure. However, researchers can go to great lengths and make every attempt to ensure accuracy in their studies, and still deal with the inherent difficulties of measuring particular events or behaviors. Sometimes, and particularly in studies of natural settings, the only measuring device available is the researcher's own observations of human interaction or human reaction to varying stimuli. As these methods are ultimately subjective in nature, results may be unreliable and multiple interpretations are possible. Three of these inherent difficulties are quixotic reliability, diachronic reliability and synchronic reliability.

Quixotic reliability refers to the situation where a single manner of observation consistently, yet erroneously, yields the same result. It is often a problem when research appears to be going well. This consistency might seem to suggest that the experiment was demonstrating perfect stability reliability. This, however, would not be the case.

For example, if a measuring device used in an Olympic competition always read 100 meters for every discus throw, this would be an example of an instrument consistently, yet erroneously, yielding the same result. However, quixotic reliability is often more subtle in its occurrences than this. For example, suppose a group of German researchers doing an ethnographic study of American attitudes ask questions and record responses. Parts of their study might produce responses which seem reliable, yet turn out to measure felicitous verbal embellishments required for "correct" social behavior. Asking Americans, "How are you?" for example, would in most cases, elicit the token, "Fine, thanks." However, this response would not accurately represent the mental or physical state of the respondents.

Diachronic reliability refers to the stability of observations over time. It is similar to stability reliability in that it deals with time. While this type of reliability is appropriate to assess features that remain relatively unchanged over time, such as landscape benchmarks or buildings, the same level of reliability is more difficult to achieve with socio-cultural phenomena.

For example, in a follow-up study one year later of reading comprehension in a specific group of school children, diachronic reliability would be hard to achieve. If the test were given to the same subjects a year later, many confounding variables would have impacted the researchers' ability to reproduce the same circumstances present at the first test. The final results would almost assuredly not reflect the degree of stability sought by the researchers.

Synchronic reliability refers to the similarity of observations within the same time frame; it is not about the similarity of things observed. Synchronic reliability, unlike diachronic reliability, rarely involves observations of identical things. Rather, it concerns itself with particularities of interest to the research.

For example, a researcher studies the actions of a duck's wing in flight and the actions of a hummingbird's wing in flight. Despite the fact that the researcher is studying two distinctly different kinds of wings, the action of the wings and the phenomenon produced is the same.

Comments on a Flawed, Yet Influential Study

An example of the dangers of generalizing from research that is inconsistent, invalid, unreliable, and incomplete is found in the Time magazine article, "On A Screen Near You: Cyberporn" (De Witt, 1995). This article relies on a study done at Carnegie Mellon University to determine the extent and implications of online pornography. Inherent to the study are methodological problems of unqualified hypotheses and conclusions, unsupported generalizations and a lack of peer review.

Ignoring the functional problems that manifest themselves later in the study, it seems that there are a number of ethical problems within the article. The article claims to be an exhaustive study of pornography on the Internet, (it was anything but exhaustive), it resembles a case study more than anything else. Marty Rimm, author of the undergraduate paper that Time used as a basis for the article, claims the paper was an "exhaustive study" of online pornography when, in fact, the study based most of its conclusions about pornography on the Internet on the "descriptions of slightly more than 4,000 images" (Meeks, 1995, p. 1). Some USENET groups see hundreds of postings in a day.

Considering the thousands of USENET groups, 4,000 images no longer carries the authoritative weight that its author intended. The real problem is that the study (an undergraduate paper similar to a second-semester composition assignment) was based not on pornographic images themselves, but on the descriptions of those images. This kind of reduction detracts significantly from the integrity of the final claims made by the author. In fact, this kind of research is commensurate with doing a study of the content of pornographic movies based on the titles of the movies, then making sociological generalizations based on what those titles indicate. (This is obviously a problem with a number of types of validity, because Rimm is not studying what he thinks he is studying, but instead something quite different. )

The author of the Time article, Philip Elmer De Witt writes, "The research team at CMU has undertaken the first systematic study of pornography on the Information Superhighway" (Godwin, 1995, p. 1). His statement is problematic in at least three ways. First, the research team actually consisted of a few of Rimm's undergraduate friends with no methodological training whatsoever. Additionally, no mention of the degree of interrater reliability is made. Second, this systematic study is actually merely a "non-randomly selected subset of commercial bulletin-board systems that focus on selling porn" (Godwin, p. 6). As pornography vending is actually just a small part of the whole concerning the use of pornography on the Internet, the entire premise of this study's content validity is firmly called into question. Finally, the use of the term "Information Superhighway" is a false assessment of what in actuality is only a few USENET groups and BBSs (Bulletin Board System), which make up only a small fraction of the entire "Information Superhighway" traffic. Essentially, what is here is yet another violation of content validity.

De Witt is quoted as saying: "In an 18-month study, the team surveyed 917,410 sexually-explicit pictures, descriptions, short-stories and film clips. On those USENET newsgroups where digitized images are stored, 83.5 percent of the pictures were pornographic" (De Witt 40).

Statistically, some interesting contradictions arise. The figure 917,410 was taken from adult-oriented BBSs--none came from actual USENET groups or the Internet itself. This is a glaring discrepancy. Out of the 917,410 files, 212,114 are only descriptions (Hoffman & Novak, 1995, p.2). The question is, how many actual images did the "researchers" see?

"Between April and July 1994, the research team downloaded all available images (3,254)...the team encountered technical difficulties with 13 percent of these images...This left a total of 2,830 images for analysis" (p. 2). This means that out of 917,410 files discussed in this study, 914,580 of them were not even pictures! As for the 83.5 percent figure, this is actually based on "17 alt.binaries groups that Rimm considered pornographic" (p. 2).

In real terms, 17 USENET groups is a fraction of a percent of all USENET groups available. Worse yet, Time claimed that "...only about 3 percent of all messages on the USENET [represent pornographic material], while the USENET itself represents 11.5 percent of the traffic on the Internet" (De Witt, p. 40).

Time neglected to carry the interpretation of this data out to its logical conclusion, which is that less than half of 1 percent (3 percent of 11 percent) of the images on the Internet are associated with newsgroups that contain pornographic imagery. Furthermore, of this half percent, an unknown but even smaller percentage of the messages in newsgroups that are 'associated with pornographic imagery', actually contained pornographic material (Hoffman & Novak, p. 3).

Another blunder can be seen in the avoidance of peer-review, which suggests that there was some political interests being served in having the study become a Time cover story. Marty Rimm contracted the Georgetown Law Review and Time in an agreement to publish his study as long as they kept it under lock and key. During the months before publication, many interested scholars and professionals tried in vain to obtain a copy of the study in order to check it for flaws. De Witt justified not letting such peer-review take place, and also justified the reliability and validity of the study, on the grounds that because the Georgetown Law Review had accepted it, it was therefore reliable and valid, and needed no peer-review. What he didn't know, was that law reviews are not edited by professionals, but by "third year law students" (Godwin, p. 4).

There are many consequences of the failure to subject such a study to the scrutiny of peer review. If it was Rimm's desire to publish an article about on-line pornography in a manner that legitimized his article, yet escaped the kind of critical review the piece would have to undergo if published in a scholarly journal of computer-science, engineering, marketing, psychology, or communications. What better venue than a law journal? A law journal article would have the added advantage of being taken seriously by law professors, lawyers, and legally-trained policymakers. By virtue of where it appeared, it would automatically be catapulted into the center of the policy debate surrounding online censorship and freedom of speech (Godwin).

Herein lies the dangerous implication of such a study: Because the questions surrounding pornography are of such immediate political concern, the study was placed in the forefront of the U.S. domestic policy debate over censorship on the Internet, (an integral aspect of current anti-First Amendment legislation) with little regard for its validity or reliability.

On June 26, the day the article came out, Senator Grassley, (co-sponsor of the anti-porn bill, along with Senator Dole) began drafting a speech that was to be delivered that very day in the Senate, using the study as evidence. The same day, at the same time, Mike Godwin posted on WELL (Whole Earth 'Lectronic Link, a forum for professionals on the Internet) what turned out to be the overstatement of the year: "Philip's story is an utter disaster, and it will damage the debate about this issue because we will have to spend lots of time correcting misunderstandings that are directly attributable to the story" (Meeks, p. 7).

As Godwin was writing this, Senator Grassley was speaking to the Senate: "Mr. President, I want to repeat that: 83.5 percent of the 900,000 images reviewed--these are all on the Internet--are pornographic, according to the Carnegie-Mellon study" ( p. 7). Several days later, Senator Dole was waving the magazine in front of the Senate like a battle flag.

Donna Hoffman, professor at Vanderbilt University, summed up the dangerous political implications by saying, "The critically important national debate over First Amendment rights and restrictions of information on the Internet and other emerging media requires facts and informed opinion, not hysteria" (p.1).

In addition to the hysteria, Hoffman sees a plethora of other problems with the study. "Because the content analysis and classification scheme are 'black boxes,'" Hoffman said, "because no reliability and validity results are presented, because no statistical testing of the differences both within and among categories for different types of listings has been performed, and because not a single hypothesis has been tested, formally or otherwise, no conclusions should be drawn until the issues raised in this critique are resolved" (p. 4).

However, the damage has already been done. This questionable research by an undergraduate engineering major has been generalized to such an extent that even the U.S. Senate, and in particular Senators Grassley and Dole, have been duped, albeit through the strength of their own desires to see only what they wanted to see.

Annotated Bibliography

American Psychological Association. (1985). Standards for educational and psychological testing. Washington, DC: Author.

This work on focuses on reliability, validity and the standards that testers need to achieve in order to ensure accuracy.

Babbie, E.R. & Huitt, R.E. (1979). The practice of social research 2nd ed . Belmont, CA: Wadsworth Publishing.

An overview of social research and its applications.

Beauchamp, T. L., Faden, R.R., Wallace, Jr., R.J. & Walters, L . ( 1982). Ethical issues in social science research. Baltimore and London: The Johns Hopkins University Press.

A systematic overview of ethical issues in Social Science Research written by researchers with firsthand familiarity with the situations and problems researchers face in their work. This book raises several questions of how reliability and validity can be affected by ethics.

Borman, K.M. et al. (1986). Ethnographic and qualitative research design and why it doesn't work. American behavioral scientist 30 , 42-57.

The authors pose questions concerning threats to qualitative research and suggest solutions.

Bowen, K. A. (1996, Oct. 12). The sin of omission -punishable by death to internal validity: An argument for integration of quantitative research methods to strengthen internal validity. Available: http://trochim.human.cornell.edu/gallery/bowen/hss691.htm

An entire Web site that examines the merits of integrating qualitative and quantitative research methodologies through triangulation. The author argues that improving the internal validity of social science will be the result of such a union.

Brinberg, D. & McGrath, J.E. (1985). Validity and the research process . Beverly Hills: Sage Publications.

The authors investigate validity as value and propose the Validity Network Schema, a process by which researchers can infuse validity into their research.

Bussières, J-F. (1996, Oct.12). Reliability and validity of information provided by museum Web sites. Available: http://www.oise.on.ca/~jfbussieres/issue.html

This Web page examines the validity of museum Web sites which calls into question the validity of Web-based resources in general. Addresses the issue that all Websites should be examined with skepticism about the validity of the information contained within them.

Campbell, D. T. & Stanley, J.C. (1963). Experimental and quasi-experimental designs for research. Boston: Houghton Mifflin.

An overview of experimental research that includes pre-experimental designs, controls for internal validity, and tables listing sources of invalidity in quasi-experimental designs. Reference list and examples.

Carmines, E. G. & Zeller, R.A. (1991). Reliability and validity assessment . Newbury Park: Sage Publications.

An introduction to research methodology that includes classical test theory, validity, and methods of assessing reliability.

Carroll, K. M. (1995). Methodological issues and problems in the assessment of substance use. Psychological Assessment, Sep. 7 n3 , 349-58.

Discusses methodological issues in research involving the assessment of substance abuse. Introduces strategies for avoiding problems with the reliability and validity of methods.

Connelly, F. M. & Clandinin, D.J. (1990). Stories of experience and narrative inquiry. Educational Researcher 19:5 , 2-12.

A survey of narrative inquiry that outlines criteria, methods, and writing forms. It includes a discussion of risks and dangers in narrative studies, as well as a research agenda for curricula and classroom studies.

De Witt, P.E. (1995, July 3). On a screen near you: Cyberporn. Time, 38-45.

This is an exhaustive Carnegie Mellon study of online pornography by Marty Rimm, electrical engineering student.

Fink, A., ed. (1995). The survey Handbook, v.1 .Thousand Oaks, CA: Sage.

A guide to survey; this is the first in a series referred to as the "survey kit". It includes bibliograpgical references. Addresses survey design, analysis, reporting surveys and how to measure the validity and reliability of surveys.

Fink, A., ed. (1995). How to measure survey reliability and validity v. 7 . Thousand Oaks, CA: Sage.

This volume seeks to select and apply reliability criteria and select and apply validity criteria. The fundamental principles of scaling and scoring are considered.

Godwin, M. (1995, July). JournoPorn, dissection of the Time article. Available: http://www.hotwired.com

A detailed critique of Time magazine's Cyberporn , outlining flaws of methodology as well as exploring the underlying assumptions of the article.

Hambleton, R.K. & Zaal, J.N., eds. (1991). Advances in educational and psychological testing . Boston: Kluwer Academic.

Information on the concepts of reliability and validity in psychology and education.

Harnish, D.L. (1992). Human judgment and the logic of evidence: A critical examination of research methods in special education transition literature . In D.L. Harnish et al. eds., Selected readings in transition.

This article investigates threats to validity in special education research.

Haynes, N. M. (1995). How skewed is 'the bell curve'? Book Product Reviews . 1-24.

This paper claims that R.J. Herrnstein and C. Murray's The Bell Curve: Intelligence and Class Structure in American Life does not have scientific merit and claims that the bell curve is an unreliable measure of intelligence.

Healey, J. F. (1993). Statistics: A tool for social research, 3rd ed . Belmont: Wadsworth Publishing.

Inferential statistics, measures of association, and multivariate techniques in statistical analysis for social scientists are addressed.

Helberg, C. (1996, Oct.12). Pitfalls of data analysis (or how to avoid lies and damned lies). Available: http//maddog/fammed.wisc.edu/pitfalls/

A discussion of things researchers often overlook in their data analysis and how statistics are often used to skew reliability and validity for the researchers purposes.

Hoffman, D. L. and Novak, T.P. (1995, July). A detailed critique of the Time article: Cyberporn. Available: http://www.hotwired.com

A methodological critique of the Time article that uncovers some of the fundamental flaws in the statistics and the conclusions made by De Witt.

Huitt, William G. (1998). Internal and External Validity . http://www.valdosta.peachnet.edu/~whuitt/psy702/intro/valdgn.html

A Web document addressing key issues of external and internal validity.

Jones, J. E. & Bearley, W.L. (1996, Oct 12). Reliability and validity of training instruments. Organizational Universe Systems. Available: http://ous.usa.net/relval.htm

The authors discuss the reliability and validity of training design in a business setting. Basic terms are defined and examples provided.

Cultural Anthropology Methods Journal. (1996, Oct. 12). Available: http://www.lawrence.edu/~bradleyc/cam.html

An online journal containing articles on the practical application of research methods when conducting qualitative and quantitative research. Reliability and validity are addressed throughout.

Kirk, J. & Miller, M. M. (1986). Reliability and validity in qualitative research. Beverly Hills: Sage Publications.

This text describes objectivity in qualitative research by focusing on the issues of validity and reliability in terms of their limitations and applicability in the social and natural sciences.

Krakower, J. & Niwa, S. (1985). An assessment of validity and reliability of the institutinal perfarmance survey . Boulder, CO: National center for higher education management systems.

Educational surveys and higher education research and the efeectiveness of organization.

Lauer, J. M. & Asher, J.W. (1988). Composition Research. New York: Oxford University Press.

A discussion of empirical designs in the context of composition research as a whole.

Laurent, J. et al. (1992, Mar.) Review of validity research on the stanford-binet intelligence scale: 4th Ed. Psychological Assessment . 102-112.

This paper looks at the results of construct and criterion- related validity studies to determine if the SB:FE is a valid measure of intelligence.

LeCompte, M. D., Millroy, W.L., & Preissle, J. eds. (1992). The handbook of qualitative research in education. San Diego: Academic Press.

A compilation of the range of methodological and theoretical qualitative inquiry in the human sciences and education research. Numerous contributing authors apply their expertise to discussing a wide variety of issues pertaining to educational and humanities research as well as suggestions about how to deal with problems when conducting research.

McDowell, I. & Newell, C. (1987). Measuring health: A guide to rating scales and questionnaires . New York: Oxford University Press.

This gives a variety of examples of health measurement techniques and scales and discusses the validity and reliability of important health measures.

Meeks, B. (1995, July). Muckraker: How Time failed. Available: http://www.hotwired.com

A step-by-step outline of the events which took place during the researching, writing, and negotiating of the Time article of 3 July, 1995 titled: On A Screen Near You: Cyberporn .

Merriam, S. B. (1995). What can you tell from an N of 1?: Issues of validity and reliability in qualitative research. Journal of Lifelong Learning v4 , 51-60.

Addresses issues of validity and reliability in qualitative research for education. Discusses philosophical assumptions underlying the concepts of internal validity, reliability, and external validity or generalizability. Presents strategies for ensuring rigor and trustworthiness when conducting qualitative research.

Morris, L.L, Fitzgibbon, C.T., & Lindheim, E. (1987). How to measure performance and use tests. In J.L. Herman (Ed.), Program evaluation kit (2nd ed.). Newbury Park, CA: Sage.

Discussion of reliability and validity as it pertyains to measuring students' performance.

Murray, S., et al. (1979, April). Technical issues as threats to internal validity of experimental and quasi-experimental designs. San Francisco: University of California. 8-12.

(From Yang et al. bibliography--unavailable as of this writing.)

Russ-Eft, D. F. (1980). Validity and reliability in survey research. American Institutes for Research in the Behavioral Sciences August , 227 151.

An investigation of validity and reliability in survey research with and overview of the concepts of reliability and validity. Specific procedures for measuring sources of error are suggested as well as general suggestions for improving the reliability and validity of survey data. A extensive annotated bibliography is provided.

Ryser, G. R. (1994). Developing reliable and valid authentic assessments for the classroom: Is it possible? Journal of Secondary Gifted Education Fall, v6 n1 , 62-66.

Defines the meanings of reliability and validity as they apply to standardized measures of classroom assessment. This article defines reliability as scorability and stability and validity is seen as students' ability to use knowledge authentically in the field.

Schmidt, W., et al. (1982). Validity as a variable: Can the same certification test be valid for all students? Institute for Research on Teaching July, ED 227 151.

A technical report that presents specific criteria for judging content, instructional and curricular validity as related to certification tests in education.

Scholfield, P. (1995). Quantifying language. A researcher's and teacher's guide to gathering language data and reducing it to figures . Bristol: Multilingual Matters.

A guide to categorizing, measuring, testing, and assessing aspects of language. A source for language-related practitioners and researchers in conjunction with other resources on research methods and statistics. Questions of reliability, and validity are also explored.

Scriven, M. (1993). Hard-Won Lessons in Program Evaluation . San Francisco: Jossey-Bass Publishers.

A common sense approach for evaluating the validity of various educational programs and how to address specific issues facing evaluators.

Shou, P. (1993, Jan.). The singer loomis inventory of personality: A review and critique. [Paper presented at the Annual Meeting of the Southwest Educational Research Association.]

Evidence for reliability and validity are reviewed. A summary evaluation suggests that SLIP (developed by two Jungian analysts to allow examination of personality from the perspective of Jung's typology) appears to be a useful tool for educators and counselors.

Sutton, L.R. (1992). Community college teacher evaluation instrument: A reliability and validity study . Diss. Colorado State University.

Studies of reliability and validity in occupational and educational research.

Thompson, B. & Daniel, L.G. (1996, Oct.). Seminal readings on reliability and validity: A "hit parade" bibliography. Educational and psychological measurement v. 56 , 741-745.

Editorial board members of Educational and Psychological Measurement generated bibliography of definitive publications of measurement research. Many articles are directly related to reliability and validity.

Thompson, E. Y., et al. (1995). Overview of qualitative research . Diss. Colorado State University.

A discussion of strengths and weaknesses of qualitative research and its evolution and adaptation. Appendices and annotated bibliography.

Traver, C. et al. (1995). Case Study . Diss. Colorado State University.

This presentation gives an overview of case study research, providing definitions and a brief history and explanation of how to design research.

Trochim, William M. K. (1996) External validity. (. Available: http://trochim.human.cornell.edu/kb/EXTERVAL.htm

A comprehensive treatment of external validity found in William Trochim's online text about research methods and issues.

Trochim, William M. K. (1996) Introduction to validity. (. Available: hhttp://trochim.human.cornell.edu/kb/INTROVAL.htm

An introduction to validity found in William Trochim's online text about research methods and issues.

Trochim, William M. K. (1996) Reliability. (. Available: http://trochim.human.cornell.edu/kb/reltypes.htm

A comprehensive treatment of reliability found in William Trochim's online text about research methods and issues.

Validity. (1996, Oct. 12). Available: http://vislab-www.nps.navy.mil/~haga/validity.html

A source for definitions of various forms and types of reliability and validity.

Vinsonhaler, J. F., et al. (1983, July). Improving diagnostic reliability in reading through training. Institute for Research on Teaching ED 237 934.

This technical report investigates the practical application of a program intended to improve the diagnoses of reading deficient students. Here, reliability is assumed and a pragmatic answer to a specific educational problem is suggested as a result.

Wentland, E. J. & Smith, K.W. (1993). Survey responses: An evaluation of their validity . San Diego: Academic Press.

This book looks at the factors affecting response validity (or the accuracy of self-reports in surveys) and provides several examples with varying accuracy levels.

Wiget, A. (1996). Father juan greyrobe: Reconstructing tradition histories, and the reliability and validity of uncorroborated oral tradition. Ethnohistory 43:3 , 459-482.

This paper presents a convincing argument for the validity of oral histories in ethnographic research where at least some of the evidence can be corroborated through written records.

Yang, G. H., et al. (1995). Experimental and quasi-experimental educational research . Diss. Colorado State University.

This discussion defines experimentation and considers the rhetorical issues and advantages and disadvantages of experimental research. Annotated bibliography.

Yarroch, W. L. (1991, Sept.). The Implications of content versus validity on science tests. Journal of Research in Science Teaching , 619-629.

The use of content validity as the primary assurance of the measurement accuracy for science assessment examinations is questioned. An alternative accuracy measure, item validity, is proposed to look at qualitative comparisons between different factors.

Yin, R. K. (1989). Case study research: Design and methods . London: Sage Publications.

This book discusses the design process of case study research, including collection of evidence, composing the case study report, and designing single and multiple case studies.

Related Links

Internal Validity Tutorial. An interactive tutorial on internal validity.

http://server.bmod.athabascau.ca/html/Validity/index.shtml

Howell, Jonathan, Paul Miller, Hyun Hee Park, Deborah Sattler, Todd Schack, Eric Spery, Shelley Widhalm, & Mike Palmquist. (2005). Reliability and Validity. Writing@CSU . Colorado State University. https://writing.colostate.edu/guides/guide.cfm?guideid=66

Reliability and Validity

Issues of research reliability and validity need to be addressed in methodology chapter in a concise manner.

Reliability refers to the extent to which the same answers can be obtained using the same instruments more than one time. In simple terms, if your research is associated with high levels of reliability, then other researchers need to be able to generate the same results, using the same research methods under similar conditions. It is noted that “reliability problems crop up in many forms.

Reliability is a concern every time a single observer is the source of data, because we have no certain guard against the impact of that observer’s subjectivity” (Babbie, 2010, p.158). According to Wilson (2010) reliability issues are most of the time closely associated with subjectivity and once a researcher adopts a subjective approach towards the study, then the level of reliability of the work is going to be compromised.

Validity of research can be explained as an extent at which requirements of scientific research method have been followed during the process of generating research findings. Oliver (2010) considers validity to be a compulsory requirement for all types of studies. There are different forms of research validity and main ones are specified by Cohen et al (2007) as content validity, criterion-related validity, construct validity, internal validity, external validity, concurrent validity and face validity.

Measures to ensure validity of a research include, but not limited to the following points:

a) Appropriate time scale for the study has to be selected;

b) Appropriate methodology has to be chosen, taking into account the characteristics of the study;

c) The most suitable sample method for the study has to be selected;

d) The respondents must not be pressured in any ways to select specific choices among the answer sets.

It is important to understand that although threats to research reliability and validity can never be totally eliminated, however researchers need to strive to minimize this threat as much as possible.

John Dudovskiy

• Babbie, E. R. (2010) “The Practice of Social Research” Cengage Learning
• Cohen, L., Manion, L., Morrison, K, & Morrison, R.B. (2007) “Research methods in education” Routledge
• Oliver, V, 2010, 301 Smart Answers to Tough Business Etiquette Questions, Skyhorse Publishing, New York USA
• Wilson, J. (2010) “Essentials of Business Research: A Guide to Doing Your Research Project” SAGE Publications

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The Significance of Validity and Reliability in Quantitative Research

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Key Takeaways:

• Types of validity to consider during quantitative research include internal, external, construct, and statistical
• Types of reliability that apply to quantitative research include test re-test, inter-rater, internal consistency, and parallel forms
• There are numerous challenges to achieving validity and reliability in quantitative research, but the right techniques can help overcome them

Quantitative research is used to investigate and analyze data to draw meaningful conclusions. Validity and reliability are two critical concepts in quantitative analysis that ensure the accuracy and consistency of the research results. Validity refers to the extent to which the research measures what it intends to measure, while reliability refers to the consistency and reproducibility of the research results over time. Ensuring validity and reliability is crucial in conducting high-quality research, as it increases confidence in the findings and conclusions drawn from the data.

This article aims to provide an in-depth analysis of the significance of validity and reliability in quantitative research. It will explore the different types of validity and reliability, their interrelationships, and the associated challenges and limitations.

In this Article:

The role of validity in quantitative research, the role of reliability in quantitative research, validity and reliability: how they differ and interrelate, challenges and limitations of ensuring validity and reliability, overcoming challenges and limitations to achieve validity and reliability, explore trusted quantitative solutions.

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Validity is crucial in maintaining the credibility and reliability of quantitative research outcomes. Therefore, it is critical to establish that the variables being measured in a study align with the research objectives and accurately reflect the phenomenon being investigated.

Several types of validity apply to various study designs; let’s take a deeper look at each one below:

Internal validity is concerned with the extent to which a study establishes a causal relationship between the independent and dependent variables. In other words, internal validity determines whether the changes observed in the conditional variable result from changes in the independent variable or some other factor.

External validity refers to the degree to which the findings of a study can be generalized to other populations and contexts. External validity helps ensure the results of a study are not limited to the specific people or context in which the study was conducted.

Construct validity refers to the degree to which a research study accurately measures the theoretical construct it intends to measure. Construct validity helps provide alignment between the study’s measures and the theoretical concept it aims to investigate.

Finally, statistical validity refers to the accuracy of the statistical tests used to analyze the data. Establishing statistical validity provides confidence that the conclusions drawn from the data are reliable and accurate.

To safeguard the validity of a study, researchers must carefully design their research methodology, select appropriate measures, and control for extraneous variables that may impact the results. Validity is especially crucial in fields such as medicine, where inaccurate research findings can have severe consequences for patients and healthcare practices.

Ensuring the consistency and reproducibility of research outcomes over time is crucial in quantitative research, and this is where the concept of reliability comes into play. Reliability is vital to building trust in the research findings and their ability to be replicated in diverse contexts.

Similar to validity, multiple types of reliability are pertinent to different research designs. Let’s take a closer look at each of these types of reliability below:

Test-retest reliability refers to the consistency of the results obtained when the same test is administered to the same group of participants at different times. This type of reliability is essential when researchers need to administer the same test multiple times to assess changes in behavior or attitudes over time.

Inter-rater reliability refers to the results’ consistency when different raters or observers monitor the same behavior or phenomenon. This type of reliability is vital when researchers are required to rely on different individuals to rate or observe the same behavior or phenomenon.

Internal consistency reliability refers to the degree to which the items or questions in a test or questionnaire measure the same construct. This type of reliability is important in studies where researchers use multiple items or questions to assess a particular construct, such as knowledge or quality of life.

Lastly, parallel forms reliability refers to the consistency of the results obtained when two different versions of the same test are administered to the same group of participants. This type of reliability is important when researchers administer different versions of the same test to assess the consistency of the results.

Reliability in research is like the accuracy and consistency of a medical test. Just as a reliable medical test produces consistent and accurate results that physicians can trust to make informed decisions about patient care, a highly reliable study produces consistent and precise findings that researchers can trust to make knowledgeable conclusions about a particular phenomenon. To ensure reliability in a study, researchers must carefully select appropriate measures and establish protocols for administering the measures consistently. They must also take steps to control for extraneous variables that may impact the results.

Validity and reliability are two critical concepts in quantitative research that significantly determine the quality of research studies. While both terms are often used interchangeably, they refer to different aspects of research. Validity is the extent to which a research study measures what it claims to measure without being affected by extraneous factors or bias. In contrast, reliability is the degree to which the research results are consistent and stable over time and across different samples , methods, and evaluators.

Designing a research study that is both valid and reliable is essential for producing high-quality and trustworthy research findings. Finding this balance requires significant expertise, skill, and attention to detail. Ultimately, the goal is to produce research findings that are valid and reliable but also impactful and influential for the organization requesting them. Achieving this level of excellence requires a deep understanding of the nuances and complexities of research methodology and a commitment to excellence and rigor in all aspects of the research process.

Ensuring validity and reliability in quantitative research is not without its challenges. Some of the factors to consider include:

1. Measuring Complex Constructs or Variables One of the main challenges is the difficulty in accurately measuring complex constructs or variables. For instance, measuring constructs such as intelligence or personality can be complicated due to their multi-dimensional nature, and it can be challenging to capture all aspects accurately.

2. Limitations of Data Collection Instruments In addition, the measures or instruments used to collect data can also be limited in their sensitivity or specificity. This can impact the study’s validity and reliability, as accurate and precise measures can lead to incorrect conclusions and unreliable results. For example, a scale that measures depression but does not include all relevant symptoms may not accurately capture the construct being studied.

3. Sources of Error and Bias in Data Collection The data collection process itself can introduce sources of error or bias, which can impact the validity and reliability of the study. For instance, measurement errors can occur due to the limitations of the measuring instrument or human error during data collection. In addition, response bias can arise when participants provide socially desirable answers, while sampling bias can occur when the sample is not representative of the studied population.

4. The Complexity of Achieving Meaningful and Accurate Research Findings There are also some limitations to validity and reliability in research studies. For example, achieving internal validity by controlling for extraneous variables may only sometimes ensure external validity or the ability to generalize findings to other populations or settings. This can be a limitation for researchers who wish to apply their findings to a larger population or different contexts.

Additionally, while reliability is essential for producing consistent and reproducible results, it does not guarantee the accuracy or truth of the findings. This means that even if a study has reliable results, it may still need to be revised in terms of accuracy. These limitations remind us that research is a complex process, and achieving validity and reliability is just one part of the giant puzzle of producing accurate and meaningful research.

Researchers can adopt various measures and techniques to overcome the challenges and limitations in ensuring validity and reliability in research studies.

One such approach is to use multiple measures or instruments to assess the same construct. In addition, various steps can help identify commonalities and differences across measures, thereby providing a more comprehensive understanding of the construct being studied.

Inter-rater reliability checks can also be conducted to ensure different raters or observers consistently interpret and rate the same data. This can reduce measurement errors and improve the reliability of the results. Additionally, data-cleaning techniques can be used to identify and remove any outliers or errors in the data.

Finally, researchers can use appropriate statistical methods to assess the validity and reliability of their measures. For example, factor analysis identifies the underlying factors contributing to the construct being studied, while test-retest reliability helps evaluate the consistency of results over time. By adopting these measures and techniques, researchers can crease t their findings’ overall quality and usefulness.

The backbone of any quantitative research lies in the validity and reliability of the data collected. These factors ensure the data accurately reflects the intended research objectives and is consistent and reproducible. By carefully balancing the interrelationship between validity and reliability and using appropriate techniques to overcome challenges, researchers protect the credibility and impact of their work. This is essential in producing high-quality research that can withstand scrutiny and drive progress.

Are you seeking a reliable and valid way to collect, analyze, and report your quantitative data? Sago’s comprehensive quantitative solutions provide you the peace of mind to conduct research and draw meaningful conclusions.

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• How to Determine the Validity and Reliability of an Instrument

How to Determine the Validity and Reliability of an Instrument By: Yue Li

Validity and reliability are two important factors to consider when developing and testing any instrument (e.g., content assessment test, questionnaire) for use in a study. Attention to these considerations helps to insure the quality of your measurement and of the data collected for your study.

Understanding and Testing Validity

Validity refers to the degree to which an instrument accurately measures what it intends to measure. Three common types of validity for researchers and evaluators to consider are content, construct, and criterion validities.

• Content validity indicates the extent to which items adequately measure or represent the content of the property or trait that the researcher wishes to measure. Subject matter expert review is often a good first step in instrument development to assess content validity, in relation to the area or field you are studying.
• Construct validity indicates the extent to which a measurement method accurately represents a construct (e.g., a latent variable or phenomena that can’t be measured directly, such as a person’s attitude or belief) and produces an observation, distinct from that which is produced by a measure of another construct. Common methods to assess construct validity include, but are not limited to, factor analysis, correlation tests, and item response theory models (including Rasch model).
• Criterion-related validity indicates the extent to which the instrument’s scores correlate with an external criterion (i.e., usually another measurement from a different instrument) either at present ( concurrent validity ) or in the future ( predictive validity ). A common measurement of this type of validity is the correlation coefficient between two measures.

Often times, when developing, modifying, and interpreting the validity of a given instrument, rather than view or test each type of validity individually, researchers and evaluators test for evidence of several different forms of validity, collectively (e.g., see Samuel Messick’s work regarding validity).

Understanding and Testing Reliability

Reliability refers to the degree to which an instrument yields consistent results. Common measures of reliability include internal consistency, test-retest, and inter-rater reliabilities.

• Internal consistency reliability looks at the consistency of the score of individual items on an instrument, with the scores of a set of items, or subscale, which typically consists of several items to measure a single construct. Cronbach’s alpha is one of the most common methods for checking internal consistency reliability. Group variability, score reliability, number of items, sample sizes, and difficulty level of the instrument also can impact the Cronbach’s alpha value.
• Test-retest measures the correlation between scores from one administration of an instrument to another, usually within an interval of 2 to 3 weeks. Unlike pre-post tests, no treatment occurs between the first and second administrations of the instrument, in order to test-retest reliability. A similar type of reliability called alternate forms , involves using slightly different forms or versions of an instrument to see if different versions yield consistent results.
• Inter-rater reliability checks the degree of agreement among raters (i.e., those completing items on an instrument). Common situations where more than one rater is involved may occur when more than one person conducts classroom observations, uses an observation protocol or scores an open-ended test, using a rubric or other standard protocol. Kappa statistics, correlation coefficients, and intra-class correlation (ICC) coefficient are some of the commonly reported measures of inter-rater reliability.

Developing a valid and reliable instrument usually requires multiple iterations of piloting and testing which can be resource intensive. Therefore, when available, I suggest using already established valid and reliable instruments, such as those published in peer-reviewed journal articles. However, even when using these instruments, you should re-check validity and reliability, using the methods of your study and your own participants’ data before running additional statistical analyses. This process will confirm that the instrument performs, as intended, in your study with the population you are studying, even though they are identical to the purpose and population for which the instrument was initially developed. Below are a few additional, useful readings to further inform your understanding of validity and reliability.

Resources for Understanding and Testing Reliability

• American Educational Research Association, American Psychological Association, & National Council on Measurement in Education. (1985).  Standards for educational and psychological testing . Washington, DC: Authors.
• Bond, T. G., & Fox, C. M. (2001). Applying the Rasch model: Fundamental measurement in the human sciences . Mahwah, NJ: Lawrence Erlbaum.
• Cronbach, L. (1990).  Essentials of psychological testing .   New York, NY: Harper & Row.
• Carmines, E., & Zeller, R. (1979).  Reliability and Validity Assessment . Beverly Hills, CA: Sage Publications.
• Messick, S. (1987). Validity . ETS Research Report Series, 1987: i–208. doi: 10.1002/j.2330-8516.1987.tb00244.x
• Liu, X. (2010). Using and developing measurement instruments in science education: A Rasch modeling approach . Charlotte, NC: Information Age.
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Validity and Reliability

The principles of validity and reliability are fundamental cornerstones of the scientific method.

This article is a part of the guide:

• Types of Validity
• Definition of Reliability
• Content Validity
• Construct Validity
• External Validity

Browse Full Outline

• 1 Validity and Reliability
• 2 Types of Validity
• 3.1 Population Validity
• 3.2 Ecological Validity
• 4 Internal Validity
• 5.1.1 Concurrent Validity
• 5.1.2 Predictive Validity
• 6 Content Validity
• 7.1 Convergent and Discriminant Validity
• 8 Face Validity
• 9 Definition of Reliability
• 10.1 Reproducibility
• 10.2 Replication Study
• 11 Interrater Reliability
• 12 Internal Consistency Reliability
• 13 Instrument Reliability

Together, they are at the core of what is accepted as scientific proof, by scientist and philosopher alike.

By following a few basic principles, any experimental design will stand up to rigorous questioning and skepticism.

What is Reliability?

The idea behind reliability is that any significant results must be more than a one-off finding and be inherently repeatable .

Other researchers must be able to perform exactly the same experiment , under the same conditions and generate the same results. This will reinforce the findings and ensure that the wider scientific community will accept the hypothesis .

Without this replication of statistically significant results , the experiment and research have not fulfilled all of the requirements of testability .

This prerequisite is essential to a hypothesis establishing itself as an accepted scientific truth.

For example, if you are performing a time critical experiment, you will be using some type of stopwatch. Generally, it is reasonable to assume that the instruments are reliable and will keep true and accurate time. However, diligent scientists take measurements many times, to minimize the chances of malfunction and maintain validity and reliability.

At the other extreme, any experiment that uses human judgment is always going to come under question.

For example, if observers rate certain aspects, like in Bandura’s Bobo Doll Experiment , then the reliability of the test is compromised. Human judgment can vary wildly between observers , and the same individual may rate things differently depending upon time of day and current mood.

This means that such experiments are more difficult to repeat and are inherently less reliable. Reliability is a necessary ingredient for determining the overall validity of a scientific experiment and enhancing the strength of the results.

Debate between social and pure scientists, concerning reliability, is robust and ongoing.

What is Validity?

Validity encompasses the entire experimental concept and establishes whether the results obtained meet all of the requirements of the scientific research method.

For example, there must have been randomization of the sample groups and appropriate care and diligence shown in the allocation of controls .

Internal validity dictates how an experimental design is structured and encompasses all of the steps of the scientific research method .

Even if your results are great, sloppy and inconsistent design will compromise your integrity in the eyes of the scientific community. Internal validity and reliability are at the core of any experimental design.

External validity is the process of examining the results and questioning whether there are any other possible causal relationships.

Control groups and randomization will lessen external validity problems but no method can be completely successful. This is why the statistical proofs of a hypothesis called significant , not absolute truth.

Any scientific research design only puts forward a possible cause for the studied effect.

There is always the chance that another unknown factor contributed to the results and findings. This extraneous causal relationship may become more apparent, as techniques are refined and honed.

If you have constructed your experiment to contain validity and reliability then the scientific community is more likely to accept your findings.

Eliminating other potential causal relationships, by using controls and duplicate samples, is the best way to ensure that your results stand up to rigorous questioning.

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Martyn Shuttleworth (Oct 20, 2008). Validity and Reliability. Retrieved Aug 20, 2024 from Explorable.com: https://explorable.com/validity-and-reliability

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Validity and Reliability of the Research Instrument; How to Test the Validation of a Questionnaire/Survey in a Research

• January 2016
• SSRN Electronic Journal 5(3):28-36

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Research methods validity reliability explained.

Home » Research Methods Validity Reliability Explained

Evaluation metrics play a critical role in the assessment of research methods, directly impacting the validity and reliability of findings. Effective evaluation metrics serve as benchmarks for determining the quality and effectiveness of research designs. Understanding these metrics helps researchers articulate the strength of their conclusions and the trustworthiness of their data sources.

In this section, we will explore various evaluation metrics prevalent in research methodologies. We will discuss their significance, how they can be measured, and their implications for ensuring credible results. By grasping these concepts, researchers can enhance their understanding of the scientific process and improve the quality of their work in delivering valuable insights.

Validity: A Key Evaluation Metric in Research

Validity plays a critical role as an evaluation metric in research. It refers to the accuracy and relevance of the conclusions drawn from data and insights. Understanding validity helps researchers to assess whether their methods truly measure what they intend to measure. If a study lacks validity, the results may lead to misguided interpretations or inappropriate applications, ultimately undermining the value of the research undertaken.

Moreover, several types of validity can be identified, each contributing to the robustness of the findings. These include construct validity, which assesses if the measurement truly reflects the theoretical concepts, and external validity, which evaluates the generalizability of the results to broader contexts. Content validity ensures that the measures adequately cover the domain of interest. By focusing on these key aspects, researchers can enhance the reliability of their conclusions and strengthen the overall quality of their evaluation metrics.

Types of Validity

Validity in research encompasses various types that help assess the effectiveness of evaluation metrics. The most prominent types include internal validity, external validity, construct validity, and statistical conclusion validity. Internal validity refers to the degree to which changes in the dependent variable can be attributed to the independent variable rather than other factors. External validity assesses the generalizability of the study findings to real-world settings or populations. Construct validity evaluates whether a test truly measures the concept it claims to measure. Lastly, statistical conclusion validity examines the appropriateness of the statistical analysis used to support conclusions.

Understanding these types of validity is crucial for any research undertaking. They provide a structured framework to ensure the credibility and reliability of findings. Good evaluation metrics will take these modalities into account, facilitating a comprehensive understanding of the data. By maintaining a keen awareness of these validity types, researchers can design better studies and derive more reliable conclusions from their work.

Ensuring Validity in Research

To ensure validity in research, it is essential to implement effective evaluation metrics. These metrics serve as benchmarks to assess the accuracy and reliability of findings. Firstly, clarity in research questions aids in aligning metrics with desired outcomes. A well-defined question gives direction to the research and ensures that relevant data is collected. Secondly, choosing appropriate research methods contributes significantly to validity. Quantitative methods may require statistical evaluation, while qualitative approaches often depend on thematic interpretations.

Furthermore, maintaining consistency in data collection is crucial. This involves using standardized tools and procedures to minimize variability. Thirdly, peer review processes can bolster validity by offering external perspectives on research designs and methodologies. Lastly, triangulation of data sources enhances the robustness of findings. By combining multiple sources or types of data, researchers can cross-verify information and strengthen the study’s conclusions. Employing these strategies not only elevates the research quality but also instills trust in the results obtained.

Reliability: The Second Pillar of Evaluation Metrics in Research

Reliability plays a crucial role in the domain of evaluation metrics, forming the second pillar in the assessment of research quality. It refers to the consistency of a measurement process, ensuring that repeated observations yield similar results. High reliability means that researchers can trust their tools and methods to produce stable and accurate results over time. Consequently, this consistency helps build confidence in the findings and conclusions drawn from research.

To assess reliability effectively, several approaches can be utilized. First, internal consistency measures how well items within a test correlate with one another, ensuring that they measure the same construct. Second, test-retest reliability evaluates stability over time by comparing scores from the same subjects across different instances. Lastly, inter-rater reliability examines the extent to which different observers agree on their observations, which is particularly important in qualitative research. Understanding and applying these reliability measures strengthens the overall validity of evaluation metrics in research.

Types of Reliability

Reliability in research is crucial for validating results, and it can be categorized into different types. These types each serve a unique purpose in ensuring that the data collected in a study is consistent and trustworthy. For instance, internal consistency examines whether various items in a measurement tool yield similar results, while test-retest reliability assesses the stability of results over time. Inter-rater reliability focuses on the degree of agreement between different observers measuring the same phenomenon.

Understanding these types not only enhances the integrity of evaluation metrics but also aids researchers in selecting the appropriate methods for their studies. By clearly identifying the various forms of reliability, researchers can improve the accuracy and credibility of their findings. This ultimately leads to more effective insights, empowering organizations to make informed decisions based on solid research outcomes.

Enhancing Reliability in Research

Reliability in research is vital for producing credible and trustworthy results. To enhance reliability, it's essential to establish clear evaluation metrics that guide the assessment of research findings. These metrics will help ensure that the methods used are consistent and produce stable outcomes across multiple trials. By adhering to robust evaluation metrics, researchers can effectively manage variability and minimize errors within their studies.

To achieve improved reliability, consider the following approaches: First, standardize procedures to eliminate inconsistencies. Consistent data collection methods minimize variability and enhance comparability. Second, utilize pilot testing to identify potential issues in the research design before full-scale implementation. This step provides an opportunity to adjust the methods and refine evaluation metrics. Finally, engage in regular peer reviews and consultations to gain insights and constructive feedback. By implementing these strategies, researchers enhance the reliability of their work, leading to more accurate and valid conclusions.

Conclusion: Seamless Evaluation Metrics in Research Methods

Seamless evaluation metrics play a crucial role in enhancing research methods by ensuring both validity and reliability in findings. By establishing clear criteria to assess data quality, researchers can better gauge the effectiveness of their methods. This not only aids in deriving meaningful insights but also enables a deeper understanding of the participants involved in the study. The interplay of time efficiency, insight quality, and thematic consistency becomes pivotal in obtaining accurate results.

Moreover, effective evaluation metrics foster a robust feedback loop, allowing researchers to refine their approaches continually. As insights are gathered and analyzed, the ability to connect patterns across different participants can lead to more comprehensive conclusions. Thus, seamless evaluation metrics empower researchers to make informed decisions, ultimately elevating the quality and trustworthiness of their research outcomes.

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The technology behind SuperBench is sophisticated and tailored to address the unique challenges cloud AI infrastructures pose. The Validator component of SuperBench conducts a series of benchmarks on specified nodes, learning to distinguish between normal and defective performance by analyzing the cumulative distribution of benchmark results. This approach ensures that even slight deviations in performance, which could indicate a potential problem, are detected early. Meanwhile, the Selector component balances the trade-off between validation time and the possible impact of incidents. Using a probability model to predict the likelihood of incidents, the Selector determines the optimal time to run specific benchmarks. This ensures that validation is performed when it is most likely to prevent issues.

The effectiveness of SuperBench is demonstrated by its deployment in Azure’s production environment, where it has been used to validate hundreds of thousands of GPUs. Through rigorous testing, SuperBench has been shown to increase the mean time between incidents (MTBI) by up to 22.61 times. By reducing the time required for validation and focusing on the most critical components, SuperBench has decreased the cost of validation time by 92.07% while simultaneously increasing user GPU hours by 4.81 times. These impressive results highlight the system’s ability to detect and prevent performance issues before they impact end-to-end workloads.

In conclusion, SuperBench, by focusing on the early detection and resolution of hidden degradations, offers a robust solution to the complex challenge of ensuring the continuous and reliable operation of large-scale AI services. The system’s ability to identify subtle performance regressions and optimize the validation process makes it an invaluable tool for cloud service providers looking to enhance the reliability of their AI infrastructures. With SuperBench, Microsoft has set a new standard for cloud infrastructure maintenance, ensuring that AI workloads can be executed with minimal disruption and maximum efficiency, thus maintaining high-performance standards in a rapidly evolving technological landscape.

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