Uses and Abuses of Coefficient Alpha

The article addresses some concerns about how coefficient alpha is reported and used. It also shows that alpha is not a measure of homogeneity orunidimensionality. This fact and the finding that test length is related to reliability may cause significant misinterpretations of measures when alpha is used as evidence that a measure isunidimensional. For multidimensional measures, use of alpha as the basis for corrections for attenuation causes overestimates of true correlation. Satisfactory levels of alpha depend on test use and interpretation. Even relatively low (e.g.,.50) levels of criterion reliability do not seriously attenuate validity coefficients. When reporting intercorrelations among measures that should be discriminable, it is important to present observed correlations, appropriate measures of reliability, and correlations corrected for unreliability. Presentation of coefficient alpha (hereinafter alpha; Cron-bach, 1951) as an index of the internal consistency or reliability of psychological measures has become routine practice in vir-tually all psychological and social science research in which multiple-item easures of a construct are used. In this article I describe four ways in which researchers ' use of alpha to conve