Alpha, Omega, and H Internal Consistency Reliability Estimates: Reviewing These Options and When to Use Them

Abstract

Reliability evidence of test scores is essential in counseling research and program evaluation, as the quality of client care is, in part, based on the proper interpretation of test scores. Cronbach’s coefficient alpha is unquestionably the most frequently reported estimate of internal consistency reliability in counseling research. For over a decade scholars in other disciplines have raised a number of concerns about the utility of coefficient alpha for capturing the reliability of psychological traits, in favor of composite reliability estimates. However, coefficient alpha remains the most dominant reliability index in counseling research. To this end, this article provides a non-technical summary of coefficient alpha, coefficient omega, hierarchical omega, and coefficient H, guidelines for their appropriate usage, and can serve as a reference for counseling practitioners and researchers when conducting outcome research and program evaluation.