Bioequivalence and Bioavailability Forum

Hi BEQool,

❝ I am not exactly looking for the standard error of the treatment difference but instead for its standard deviation. I am using Phoenix WinNonlin and standard error of the treatment difference is already given with "Diff_SE". I would like to find out how to get (if it is possible) standard deviation of the treatment difference from the standard error of the treatment difference "Diff_SE" (or is there some other way?).

Yeah, that is confusing, too.
We have all kinds of standard deviations, but the one we usually learn about is the standard deviation of a sample.
But if we have a sample, then we also have a mean from it, and the standard deviation of that mean is called a standard error. When statisticians derive a standard deviation of a mean (in contrast to a sample), then they tend to call that a standard error. My suspicion is they are solely doing it to confuse people like me. So, I think the answer to your question is that the SE of the difference is the standard deviation of the difference.

I can't help with WNL at all. What it does, how it does it and how it presents results to the user is entirely outside my competences.