SAS and SPSS Macros to Calculate Standardized Cronbach’s Alpha Using the Upper Bound of the Phi Coefficient for Dichotomous Items

Document Type



Community and Global Health (CGU)

Publication Date



Psychology | Social and Behavioral Sciences


Cronbach’s α is widely used in social science research to estimate the internal consistency of reliability of a measurement scale. However, when items are not strictly parallel, the Cronbach’s α coefficient provides a lower-bound estimate of true reliability, and this estimate may be further biased downward when items are dichotomous. The estimation of standardized Cronbach’s α for a scale with dichotomous items can be improved by using the upper bound of coefficient ϕ. SAS and SPSS macros have been developed in this article to obtain standardized Cronbach’s α via this method. The simulation analysis showed that Cronbach’s α from upper-bound ϕ might be appropriate for estimating the real reliability when standardized Cronbach’s α is problematic.

Rights Information

© 2007 Psychonomic Society, Inc.