To compute Cronbach's alpha for a set of variables, use the ALPHA option in PROC CORR as follows:
PROC CORR DATA=dataset ALPHA;
SAS website provides an example about calculating the Cronbach's alpha.
Very often, 95% confidence interval may be required, the calculation is not straightforward, but there are SAS macros available from the SAS web site.
Some references about Cronbach's alpha can be found below:
To assess the reliability of an instrument, the good reliability features include:
- Internal consistency = Cronbach's alpha >= 0.70 for new measures
- Stability = reliability coefficient >= 0.70
- Equivalence = Kappa statistic >= 0.61
In one of comments on FDA's guidance on PROM (patient reported outcome measures), Cronbach's alpha was cited to measure Internal Consistency and construct validity (with scale analysis) - Cronbach's alpha > 0.70