Composite Reliability Index Calculation

00:00 4 marks

A researcher developed a new questionnaire to measure social anxiety. To assess its reliability, they used two methods: test-retest reliability and internal consistency. The test-retest reliability, conducted two weeks apart, yielded a correlation coefficient of 0.80. The internal consistency, measured using Cronbach’s alpha, was found to be 0.75.

To obtain a more comprehensive measure of reliability, a composite reliability index is calculated by weighting the test-retest reliability at 60% and the internal consistency at 40%.

(a) Calculate the composite reliability index for this questionnaire.

(b) Explain why a weighted average is used to combine these reliability measures. Discuss one limitation of using a weighted average in this context.

Hint Hint

Hint

For part (a), remember to multiply each reliability measure by its assigned weight before summing. For part (b), consider the different aspects of reliability each measure captures and the potential oversimplification of a weighted average.

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Answer Answer

Complete Answer

Part (a): Composite reliability index = 0.78; Part (b): Weighted average reflects the relative importance of each reliability type, but assumes measures are commensurable and may not capture complex interactions.

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