I have a general question of unbalanced data. I'm performing a T test on Group A and Group B. Group A has 20 data while Group B has 500. I set unequal variance (Welch) for the adjustment and the P-value is 0.01. Can I conclude that there is significance? I have another idea that I'm not sure about. I randomly select about 20 samples from Group B multiple times and test against the Group A. Should I do some adjustment for the result? I am not sure if this is works or not. If it works, what kind of adjustment I should use for multi-testing? Thank you! I appreciate any replies!
Multiple testing of unbalanced data by R
statistics;unbalanced classes
it does not have anything to do with whether t test or welch t test. As long as your group A samples estimate the mean and standard deviation of population A very well, and group B samples estimate the mean and standard deviation of population B very well, then there shouldn't be any problem. If the SD of population A is assumed different from that of population B, then you better go welch t test. Your question may be better asked at cross-validated, who cares more statistics, I think.