But this is why you have to determine variances and homogeneity of the samples first. Also, different formula apply depending on this criteria. You can't just d

But this is why you have to determine variances and homogeneity of the samples first. Also, different formula apply depending on this criteria. You can't just do a T-test without any knowledge about control and test groups. (Or you would have to assume the worst case, anyways, meaning, you'll need huge amounts of data.)