>That's always the problem: When you don't have a very good understanding of the mechanism and all the consequences you have to be lucky that the population you study is more or less the correct one. You don't even know when you got the wrong one. If the drug - but same in any other field that uses statistics - fails for 95% of people you may still have a hit for a sub-population (it's not as easy as "it's the other 5%" of course).
Good point, but this kind of subgroup analysis also runs into the multiple comparisons problem. If you test all kinds of subgroups (or just do a lot of any kind of tests), chances are good that you will run into false positives. In such scenarios, it becomes more probable than not that a given positive result is in fact false. Combine that with the base-rate fallacy (the good majority of drug trials yield null results, but this is not taken into account) and you are in really bad shape.
There was a replication study a while ago that tried to replicate IIRC 50 or so "landmark" cancer studies, and only came up with significant results in 6 cases.
Bayesian methods go a long way towards solving these issues, but there is no cure for low-power studies. They just can't tell you much, and will lead you heavily astray if you don't properly account for multiple comparisons, etc.
>Over the years I have gotten much more skeptical of all statistics based "knowledge". Reading those studies always leaves a strange taste in my mouth. Something doesn't feel right. It does not taste like knowledge. I see the relevance given that it often is the only way to make practical progress of course.
Clinical studies of new drugs have uncertainty. Thus any decision-making based on results must take this uncertainty into account. You can't get away from statistics here. The bad feeling in your mouth may be from the unintuitive and usually inappropriate use of P-values and null-hypothesis statistical tests. The vast majority of researchers are actually completely mistaken on what P-values even mean. Most think that they are "the chance of a false positive" or something similar, which is completely wrong.
Bayesian methods help here, because they are the only valid way of combining past information with new information.