Posted on: 4th Apr 2020 3191 Views

Types of Reliability in Research

Types of Reliability in research is basically an extent up to which a specific research method is able to produce the same outcomes when you apply it in the same situations and by using a similar sample. The different types of reliability are:

Types of Reliability in Research
Types of reliabilityMeasure of consistency
Test-retestSimilar tests over time.
Inter-raterSimilar tests performed by different people
Parallel  formsVarious version of the test  that is created
Internal consistencyA single item of a test


  1. It is very much essential for you to consider reliability at the time of developing a research design, collection, and analysis of facts.
  2. You can determine the types of reliability to be utilizing consideration of the type of research and methodology utilized for performing an investigation.

Different Types of Reliability: Techniques to Measure Them

The 4 different types of reliability and techniques to measure them are:

1. Test-retest reliability

It helps in measuring the consistency in research outcomes if a similar test is repeated by using the same sample over a period of time.  You can utilize test-retest reliability when you think that result will remain constant.

Example:  Before performing research you expect that a test that you will perform to test the color blindness of trainee pilots would have high test-retest reliability.  As color blindness is a trait that does not change over a period of time.

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A. How to measure test-retest reliability?

You need to perform similar tests on a similar group of people at different times.  After that, you need to compute the correlation between two sets of outcomes.

B. Importance of Test-retest reliability

Test-retest reliability is a type of reliability that has great significance as there might be many variables that can influence the research outcomes at various points in time.

For example:  Participants participating in research might have different moods. Changes in external situations might have an effect on the mood of participants.

You can use test-retest reliability for assessing the effectiveness of research methods over a period of time. The less variation between the two sets of research outcomes. Less difference between two different outcomes means high test-retest reliability.

Example of Test-retest reliability: Test-retest is a type of reliability where researchers can design a questionnaire for measuring the IQ level of people participating in research.

After two months gain investigator has performed the same test on a similar group of people but the outcomes generate were totally different.  As there is a difference in two research results, therefore, test-retest reliability is low.

C. Techniques for improving test-retest reliability

A few techniques that you can apply for improving the test-retest reliability are:

  • At the time of preparing the questionnaire, you should design questions in such a manner that the mood of the respondent does not get influenced.
  • When making a plan for the selection of research methods for the collection of information, you should not get influenced by external factors. It is very much important for you to ensure that all the samples you have tested are in similar circumstances.

You can expect changes in participants over a period of time.

2. Inter-rater Reliability

It is also recognized to be as inter-observer reliability. Inter-rater reliability helps in measuring the level of agreement among the number of people assessing a similar thing.  It is considered an alternative form of reliability.  You can utilize inter-rater reliability when investigators collect facts by giving ratings or scores to different variables of the study.

  • Note: Inter-rater reliability is very crucial in research which includes observation techniques. In other words, inter-rater reliability is essential in studies where you intend to collect facts through observing things.

A. Importance

Inter-rater reliability is very much crucial as it helps in minimizing the subjectivity so that the other investigator can easily again conduct research for getting similar outcomes. It is very much essential for you to ensure that different people might have their own criteria for rating the variables.

Inter-rater reliability is very much crucial, especially in such a situation where there are a number of investigators involved in research for the accumulation and analysis of facts.

Inter-rater reliability: Example

An investigation performs by the number of researchers for analyzing the progress of the healing of wounds on patients.  A specific criterion has been set by the researcher for recording and assessing the different aspects of the wound.

A comparison between the results which different investigators checking the same patient has generated represents that there is a strong correlation between different set of outcomes. This means that the Test which the researcher has performed for assessing the patient has high inter-rater reliability.

B. How to measure?

You along with other investigators need to observe a similar sample. After that, you need to compute the correlation between different sets of outcomes.  In case all investigator provides a similar rating that means a test has high inter-rater reliability.

C. Techniques to improve it

Some techniques which you can adopt for improving inter-rater reliability are:

  • You need to clearly define the variables of your study and the methodology which you will utilize for measuring it.
  • Set proper criteria for analyzing the way you will rate different variables.
  • In case a number of investigators are observing similar things then you need to make sure that all researchers have information and access to training.

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3. Parallel forms Reliability

It is a type of reliability that you can utilize for measuring the correlations between two similar versions of the test. Researchers can use different assessment tools in order to design questions for measuring similar things.

A. Significance of Parallel form of reliability

The parallel form of reliability is very crucial in order to avoid respondents giving the same answers. It is very much essential for you to ensure that all Questions produce reliable outcomes.

B. How to measure it?

One of the best techniques to measure the parallel form of reliability is to create a large set of questions for doing the evaluation of similar things.  Then you need to categorize these questions into two on a random basis.

After obtaining the answers to two different sets of questions you need to compute the correlation between the outcomes. A high level of correlation between answers to two sets of questions represents a high parallel form of reliability.

  • Note: In the context of research in the educational field, it is very much important for you to develop a unique version of tests for making sure that students do not have access to research questions in advance. A parallel form of reliability represents that if a similar group of students uses two different versions for reading a comprehensive test then there are high chances that students will get the same outcomes in both tests.

A high parallel form of reliability: Example The researcher has a design a set of questions for measuring financial risk faced by a group of people.  An investigator has utilized random technique for categorizing the questions in two sets.

You can divide participants also in two groups.  The researcher has assign group A with one test and group b with another test. After that researcher makes a comparison between outcomes and it has been found that results are identical which indicates a high parallel form of reliability.

C. Techniques for improving parallel forms of reliability

In order to improve the parallel form of reliability need to make sure that all questions are designed using one single theory.

4. Internal consistency

It is a type of reliability that helps in assessing the correlation between numbers of items in a test that are intended to measure a similar construct. There is no need for computing internal consistency without making repetition of the test or engagement of other investigators.  If you have only a single data set then you can use internal consistency measures for measuring reliability.

A. Why internal consistency is important?

Internal consistency is very much essential especially in a case when you are formulating questions, at that time it is very much essential for you to ensure that all the items reflect a similar thing. If in case people respond related to a different thing matches it represents unreliable outcomes.

A researcher design questions a questionnaire consisting of close an ended question that consists of only two options agree or disagree. It is internal consistency that will help you in determining whether all the statements are reliable or not.

B. How to calculate internal consistency?

There are basically two basic methods that you can use for measuring internal consistency these are:

  • Average inter-item correlation:  It is basically a technique that you can utilize for assessing a similar construct. You need to first compute the correlation between outcomes of all possible pairs and then you need to perform a calculation for finding an average.
  • Split half reliability: By using the random technique you can divide a set of measures into two sets. After performing a test on all the sets of respondents, you should compute the correlation between different sets of responses.

Example of internal consistency: A specific team of people is provided with a set of states whose purpose is to measure a pessimistic and optimistic mindset.

You need to rate every agreement consisting range of been 1 to 5. If the respondent provides high ratings to the indicator of optimism and low rating to pessimism.  A researcher has computed correlation and it has been found that all the ratings are in favor of optimism which indicates low internal consistency.

C. How to improve internal consistency

You for improving internal consistency need to pay special attention to Planning design for research in order to collect and analyze data. It is a type of research and methodology that helps you determine g the types of research reliability you should utilize.


It has been concluded from the above is that considering research designed methodology is very helpful in relation to determining the kind of reliability applicable to your research. Other acts that have been discovered that decisions related to types of reliability to be sued in research are based on types of research and methods.

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