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Reliability Analysis

Reliability can be explained as the consistency of a measure. It allows you to study the properties and items of the measurement scale. The researchers can assess the stability of measures through this method. Along with the measurement, it provides information about the individual items in the scale. This analysis makes sure that the measurements are consistent while we measure something like productivity, efficiency, knowledge etc. High reliability means higher consistent measurements over time and thus the results of the test can be trusted.

There are four ways to measure reliability:-

Split-Half Reliability Method

This analysis determines the level of error in the test results due to poor test construction. The process is as follows:-

    1. Split a test into two halves.
    2. Repeat for a large group of individuals
    3. Measurement of thecorrelation between the scores for both halves.

The highest is the correlation analysis between the two halves, the higher is the internal consistency of the test or survey.

Test-Retest Reliability Method

This analysis determines the level of error in the test results due to administration problems. The process is as follows:-

    1. Administer a test to a group of individuals.
    2. After a few days or months, administer the same test to the same group of individuals.
    3. Finally, measure the correlation between the scores of the two tests.

The correlation between the score of these tests should be at least 0.80 or higher which indicates good reliability.

Parallel Forms Reliability Method

This analysis determines the level of error in the test results due to outside effects. The process is as follows:-

    1. Administer one version of the test to a group of individuals.
    2. Later, administer the alternate but equally difficult version of the test to the same group of individuals.
    3. Measure the correlation between the scores of the two tests to check the reliability.

Inter-rater Reliability Method

In this method, multiple qualified raters or judges rate each item on a test and then calculate the overall per cent agreement between raters or judges. Here the reliability analysis is determined by the higher percentage of agreement between the judges.

Reliability & Standard Error of Measurement

Reliability coefficient R is also used to calculate a standard error of measurement.

It is calculated as:

SEm = s√1-R

where:

    1. s: The standard deviation of measurements
    2. R: The reliability coefficient of a test

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