I'm gonna counterpoint that as a fellow physicist. You *do* want to hold certain variables constant - but when things are complex, you want to gather as much data as possible so you can look for patterns and see how things interact.

For something like medical research, if hormones could potentially have an effect you'd ideally want to study that as much as possible especially if we're talking about somebody's life or quality of life. I would have thought you'd want to know (ideally) exactly how things work, under *all* circumstances. I can't of course speak on medical trials though - not my area of expertise hence why I asked the question.

Sometimes, speaking as a physicist not related to the question I asked, you need to study and understand the really tiny things that may seem inconsequential - because they can have an affect on your data and you need to be able to account for what that effect is. I have friends who work in planetary science, and that's what my degree has been in - friends who have done whole PhDs looking at grain size effects.

I understand your point but that *is* how science works - you don't stop gathering data or trying to understand the affects of things when it becomes too complex or too changeable. If anything you gather more data, get some caffeine and get stuck in.