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Reliability and Validity – Definitions, Types & Examples
Published by Alvin Nicolas at August 16th, 2021 , Revised On October 26, 2023
A researcher must test the collected data before making any conclusion. Every research design needs to be concerned with reliability and validity to measure the quality of the research.
What is Reliability?
Reliability refers to the consistency of the measurement. Reliability shows how trustworthy is the score of the test. If the collected data shows the same results after being tested using various methods and sample groups, the information is reliable. If your method has reliability, the results will be valid.
Example: If you weigh yourself on a weighing scale throughout the day, you’ll get the same results. These are considered reliable results obtained through repeated measures.
Example: If a teacher conducts the same math test of students and repeats it next week with the same questions. If she gets the same score, then the reliability of the test is high.
What is the Validity?
Validity refers to the accuracy of the measurement. Validity shows how a specific test is suitable for a particular situation. If the results are accurate according to the researcher’s situation, explanation, and prediction, then the research is valid.
If the method of measuring is accurate, then it’ll produce accurate results. If a method is reliable, then it’s valid. In contrast, if a method is not reliable, it’s not valid.
Example: Your weighing scale shows different results each time you weigh yourself within a day even after handling it carefully, and weighing before and after meals. Your weighing machine might be malfunctioning. It means your method had low reliability. Hence you are getting inaccurate or inconsistent results that are not valid.
Example: Suppose a questionnaire is distributed among a group of people to check the quality of a skincare product and repeated the same questionnaire with many groups. If you get the same response from various participants, it means the validity of the questionnaire and product is high as it has high reliability.
Most of the time, validity is difficult to measure even though the process of measurement is reliable. It isn’t easy to interpret the real situation.
Example: If the weighing scale shows the same result, let’s say 70 kg each time, even if your actual weight is 55 kg, then it means the weighing scale is malfunctioning. However, it was showing consistent results, but it cannot be considered as reliable. It means the method has low reliability.
Internal Vs. External Validity
One of the key features of randomised designs is that they have significantly high internal and external validity.
Internal validity is the ability to draw a causal link between your treatment and the dependent variable of interest. It means the observed changes should be due to the experiment conducted, and any external factor should not influence the variables .
Example: age, level, height, and grade.
External validity is the ability to identify and generalise your study outcomes to the population at large. The relationship between the study’s situation and the situations outside the study is considered external validity.
Also, read about Inductive vs Deductive reasoning in this article.
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Threats to Interval Validity
Threats of external validity, how to assess reliability and validity.
Reliability can be measured by comparing the consistency of the procedure and its results. There are various methods to measure validity and reliability. Reliability can be measured through various statistical methods depending on the types of validity, as explained below:
Types of Reliability
Types of validity.
As we discussed above, the reliability of the measurement alone cannot determine its validity. Validity is difficult to be measured even if the method is reliable. The following type of tests is conducted for measuring validity.
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How to Increase Reliability?
- Use an appropriate questionnaire to measure the competency level.
- Ensure a consistent environment for participants
- Make the participants familiar with the criteria of assessment.
- Train the participants appropriately.
- Analyse the research items regularly to avoid poor performance.
How to Increase Validity?
Ensuring Validity is also not an easy job. A proper functioning method to ensure validity is given below:
- The reactivity should be minimised at the first concern.
- The Hawthorne effect should be reduced.
- The respondents should be motivated.
- The intervals between the pre-test and post-test should not be lengthy.
- Dropout rates should be avoided.
- The inter-rater reliability should be ensured.
- Control and experimental groups should be matched with each other.
How to Implement Reliability and Validity in your Thesis?
According to the experts, it is helpful if to implement the concept of reliability and Validity. Especially, in the thesis and the dissertation, these concepts are adopted much. The method for implementation given below:
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 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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