SAS FAQ #29: Internal consistency statistics using SAS

Question:

I want to obtain an internal consistency index (say, Cronbach's alpha) for my questionnaire. How can I do this using SAS?

Answer:

Use PROC CORR with the ALPHA and NOMISS options. For instance:

PROC CORR ALPHA NOMISS ;
VAR var1 var2 varK ;

The ALPHA option calculates the correlation between each variable and the total of the remaining variables and calculates Cronbach's alpha using only the remaining variables. The NOMISS option will remove an observation with a missing value on any variable from the analysis. It is important to include the VAR statement so that no unwanted variables are included in the alpha analysis.

If you want just the item analysis statistics printed without the correlation matrix or the usual summary statistics generated by PROC CORR, add the NOSIMPLE and NOCORR options to the PROC CORR line.

For more information on the CORR procedure, click on the Help button in the SAS menu bar and scroll to SAS Help and Documentation.

If you have further questions, send E-mail to stats@ssc.utexas.edu.