SAS and SPSS macros to calculate standardized Cronbach's alpha using the upper bound of the phi coefficient for dichotomous items.
Cronbach's a 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 a 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 a for a scale with dichotomous items can be improved by using the upper bound of coefficient phi. SAS and SPSS macros have been developed in this article to obtain standardized Cronbach's a via this method. The simulation analysis showed that Cronbach's a from upper-bound phi might be appropriate for estimating the real reliability when standardized Cronbach's a is problematic.
Sun
Wei
W
University of Southern California, Los Angeles, California, USA. wsun@usc.edu
Chou
Chih-Ping
CP
Stacy
Alan W
AW
Ma
Huiyan
H
Unger
Jennifer
J
Gallaher
Peggy
P
D003627:Data Interpretation, Statistical; D006801:Humans; D011584:Psychology / Q000379:methods* / Q000706:statistics & numerical data*