Overview
I'm working on a statistics discussion question and need the explanation and answer to help me learn.
Suppose that for two populations that are approximately normally distributed with means M1 and M2 and standard deviations S1 and S2, you wish to test the hypothesis H0: M1=M2 versus H0: M1 != M2. Discuss how your testing procedure will differ if you assume that the population variances are:
1) known and equal;
2) known but unequal;
3) unknown and equal;
4) unknown but unequal.