On the relationship between coefficient alpha and composite reliability.

A quantitative analysis of 2,524 pairs of coefficient alpha and composite reliability values derived from empirical investigations revealed that although the average composite reliability value exceeded the average corresponding coefficient alpha value, the difference was relatively inconsequential for practical applications such as meta-analysis.

Abstract

Cronbach's coefficient alpha is the most widely used estimator of the reliability of tests and scales. However, it has been criticized as being a lower bound and hence underestimating true reliability. A popular alternative to coefficient alpha is composite reliability, which is usually calculated in conjunction with structural equation modeling. A quantitative analysis of 2,524 pairs of coefficient alpha and composite reliability values derived from empirical investigations revealed that although the average composite reliability value (.86) exceeded the average corresponding coefficient alpha value (.84), the difference was relatively inconsequential for practical applications such as meta-analysis.