Hi all, I'm trying to solve what is likely a fairly easy problem but is tripping me up. I want to chronicle the difference in means for gpa when some variables are 0 vs 1. For example, if I was doing them by hand, I could just do something like this and subtract the two means myself:

Code:
sum gpa if tutor == 0
sum gpa if tutor == 1

sum gpa if attendance == 0
sum gpa if attendance == 1

sum gpa if question == 0
sum gpa if question == 1
Any ideas for simplifying/automating this summing and subtracting of the means?