An introduction to Coefficient Alpha and Internal Consistency

Abstract

Cronbach’s α is the most widely used index of the reliability of a scale. However, its use and in- terpretation can be subject to a number of errors. This article discusses the historical develop- ment of α from other indexes of internal consistency (split-half reliability and Kuder–Richard- son 20) and discusses four myths associated with α: (a) that it is a fixed property of the scale, (b) that it measures only the internal consistency of the scale, (c) that higher values are always pre- ferred over lower ones, and (d) that it is restricted to the range of 0 to 1. It provides some recom- mendations for acceptable values of α in different situations.