For my dataset, I have two groups.
For each group I would like to perform a one-sample t-test to compare the value against 0. I would then like to test a two-sample t-test to compare the mean of each group.
Should I correct for the multiple comparison for the one-sample tests only (i.e. alpha/2) or correct for all three multiple comparisons (alpha/3)?
My issue is that if one group is found to be significantly above 0 while the other isn't, then correcting the the third multiple comparison is likely to be too conservative.
And on a related note, I need to perform similar tests for another dataset, which was derived from an entirely different population. Should I now correct for all the comparisons that were performed on the first and second datasets?