From alpha to omega: A practical solution to the pervasive problem of internal consistency estimation

TLDR

Coefficient alpha is widely used in psychological research despite well‑documented deficiencies, a mismatch stemming from users’ unfamiliarity with the literature and the lack of known alternatives. The authors review the psychometric literature on alpha and propose coefficient omega as a practical alternative. They provide a concise guide for computing point and interval estimates of omega in a free, open‑source software environment.

Abstract

Coefficient alpha is the most popular measure of reliability (and certainly of internal consistency reliability) reported in psychological research. This is noteworthy given the numerous deficiencies of coefficient alpha documented in the psychometric literature. This mismatch between theory and practice appears to arise partly because users of psychological scales are unfamiliar with the psychometric literature on coefficient alpha and partly because alternatives to alpha are not widely known. We present a brief review of the psychometric literature on coefficient alpha, followed by a practical alternative in the form of coefficient omega. To facilitate the shift from alpha to omega, we also present a brief guide to the calculation of point and interval estimates of omega using a free, open source software environment.