Reliability Analysis

Reliability Analysis

In terms of reliability, the ability of a scale to reproduce consistent results over several measurements is called reliability. The process of analysing reliability is called reliability analysis. By determining the association between scores obtained from different administrations of the scale, reliability analysis can be determined by determining the extent of systematic variation within a scale. A scale is reliable if it produces consistent results in a reliability analysis, which is high.

There are four ways to measure reliability:-

Split-Half Reliability Method

This analysis is a kind of internal consistency reliability method which determines the level of error in the test results due to poor test construction. The process is as follows:-

    1. Split the scale items into two halves on the basis of an even or odd number of items.
    2. Repeat for a large group of individuals
    3. Measurement of the correlation 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. There is a limitation to this analysis, depending on how the items are divided, the outcome of this analysis will vary. Using coefficient alpha or Cronbach’s alpha, this limitation can be avoided.

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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