In reply to Rick Wicklin.

Hi Rick,
Lisa again,
Thank you for your response, but I am still confused.
Why is it possible to use 'Y' as a binary variable in 'PROC MEANS'? In my data, if I use little y, SAS gives an error, stating that 'little y' does not exist, and when I use 'Y,' the error message is: 'Y' does not conform to the variable type.

best