Reliability vs. Validity – Understanding the Differences

08.09.22 Reliability & Validity Time to read: 5min

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Researchers use reliability vs. validity as criteria for evaluating the quality of measurement. Assigning numerical values to a set of characteristics is necessary to assess someone or something. This method generates the data we evaluate.

Reliability vs. Validity – In a Nutshell

  • Reliability vs. validity are two independent criteria researchers use to evaluate their measures.
  • Reliability is consistency over time, between items, and between researchers.
  • Validity is the degree to which the scores accurately reflect the variable they intend to assess.
  • The reliability vs. validity of measurement is not determined by a single study but rather by the pattern of results across numerous studies. The evaluation of reliability vs. validity is a continual activity.

Definition: Reliability vs. Validity

Reliability vs. validity refers to a method’s capacity to accurately measure something:

  • Reliability refers to a measure’s consistency.
  • Validity relates to a measure’s precision.
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How to Differentiate between Reliability vs. Validity

Reliability vs. validity is the criteria for evaluating the quality of research. They show the accuracy of a measurement method, methodology, or test. Validity refers to a measure’s precision, whereas reliability refers to its consistency.1

Reliability Validity
What does it tell you? The degree in which the same results are obtained when the study is repeated under identical conditions. How accurately the results measure what they're intended to measure.
How is it assessed? Examining the consistency of outcomes over time, between various observers, and within the test itself. Comparing the accuracy of the results to accepted theories and other measurements of the same idea.
How do they relate? Although the results of a reliable measurement may be reproducible, they aren't always accurate. A valid measurement is often reliable: if a test yields correct results, it should be repeatable.

Understanding Reliability vs. Validity

Reliability vs. validity are closely connected but have distinct meanings. A measurement can be reliable but not necessarily valid. However, if a measure is valid, it’s also reliable.

Understanding Reliability

Reliability refers to the consistency with which a method measures a variable. The measurement is considered reliable if the exact result can be attained consistently by employing the same techniques under the same conditions.

You conduct a series of temperature measurements on a liquid sample under the same conditions each time. Because the thermometer shows the same temperature every time, the findings may be deemed reliable.

Understanding Validity

Validity refers to the precision with which a method measures the target variable. If a study has high validity, its findings correlate to the actual traits, characteristics, and fluctuations of the physical or social reality.

A measurement’s validity may be indicated by its high reliability. If a method cannot be relied upon, it is most likely invalid.

If the thermometer displays different temperatures each time, despite carefully controlling the environment to ensure the sample’s temperature remains constant, it is likely faulty, and its results are consequently invalid.

Assessing Reliability vs. Validity

Reliability vs. validity is measured in different ways. By comparing various copies of the exact measurement, one can assess reliability. Validity is more challenging to evaluate but can be approximated by comparing the findings to relevant facts or hypotheses.

Types of Reliability

Distinct statistical methodologies allow for the estimation of various types of reliability. Below are the types of reliability vs. validity.

Type of Reliability Assessment Example
Test-Retest The consistency of measurement across time: Do repeated measures yield the same results? A group of individuals completes a questionnaire meant to assess personality traits. Test-retest reliability is high if individuals retake the questionnaire later and provide the same responses.
Interrater Do different raters come up with the same results when performing the exact measurement? Five examiners provide significantly varied evaluations for the same student's project, each based on a checklist of evaluation criteria. This suggests that the checklist's inter-rater reliability is low.
Internal Consistency Do different sections of a test that is designed to assess the same thing consistently yield the same results? You perform a survey to gauge self-esteem. If the findings are randomly split in half, they should be strongly correlated. The dissimilarity between the two outputs suggests a lack of consistency in the system.

Types of Validity

A measurement’s validity can be evaluated using three primary categories of evidence. Each type of validity is evaluable using either expert opinion or statistical approaches.

Type of Validity Assessment Example

Conformity of measurement to current theory and understanding of the concept being tested. A self-esteem questionnaire could be evaluated by evaluating other attributes known or presumed to be associated with self-esteem. A strong relationship between self-esteem ratings and associated qualities would show high construct validity.
Content The degree to which the measurement encompasses all features of the measured concept. A test designed to assess the Spanish proficiency of a group of pupils includes reading, writing, and speaking but no listening sections. Experts concur that listening is a crucial element of language ability; hence, the assessment lacks content validity for gauging the total Spanish proficiency level.

The degree to which the outcome of a measurement conforms to the results of other accurate measurements of the same notion. A survey is undertaken to determine the political views of a region's voters. If the results accurately anticipate the outcome of a subsequent election in that region, then the poll has a high criterion validity.

Ensuring Reliability vs. Validity

Your results’ reliability vs. validity depends on developing a solid research design, selecting appropriate methodologies and samples, and conducting your research with precision and consistency.

Ensuring Reliability

Throughout the process of data collection, ensuring reliability vs. validity must be considered. When collecting data with a tool or method, the results must be accurate, consistent, and repeatable.

  • Apply Your Methods Consistently
  • Plan your technique carefully to ensure that identical actions are performed for every measurement. This is particularly crucial when numerous researchers are involved.

Ensuring Validity

An accurate assessment of differences can only be made when ratings that accurately reflect the variations are used. Validity should be considered early on in the research process when deciding how to collect data.

  • Choose Appropriate Methods of Measurement
  • Ensure that your approach and measuring methodology are of excellent quality and specifically designed to measure what you wish to learn. This should be based on extensive research and current knowledge.
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Incorporating Reliability vs. Validity

Discussing reliability vs. validity in various portions of your thesis, dissertation, or research paper is appropriate. Your work is more reliable and trustworthy if you demonstrate that you considered them when arranging your research and evaluating the results.

Literature Review – Other researchers have made what efforts to develop and enhance reliability vs. validity research methods?

Methodology – How did you design your study to ensure the reliability vs. validity of the instruments used? This includes the number of samples, environmental conditions, sample preparation, and measurement methodologies.

Results – Include these numbers with your primary findings if you have calculated reliability vs. validity.

Discussion – Now is the time to discuss the reliability vs. validity of your results. Were they consistent and reflective of genuine values? If not, then why?

Conclusion – If the findings’ reliability vs. validity were a significant issue, it would be helpful to highlight this here.


The primary distinction between reliability vs. validity is reliability refers to the consistency of test results. In contrast, validity relates to the degree to which a test measures and what it claims to measure.2

A test could be reliable but invalid, but can’t be valid without being reliable. We cannot conclude that a test measures what it’s intended to measure if the measurements are inconsistent; therefore, the test is invalid.1

Validity is more difficult to evaluate than reliability; however, it’s more crucial. To acquire usable results, you must collect data using valid methodologies; the research must measure what it purports to measure. This ensures the validity of your data analysis and findings.


1 Upen. “Difference Between Validity and Reliability.” Pediaa. August 22, 2018.

2 Major Movements in Psychology. “Can you have reliability without validity?.” Accessed August 29, 2022.