Why the 3? Earlier in the morning I was reading one of the latest posts published by John D. Cook about dose finding studies. I am well aware of the 3+3 design. Incidentally, I attended a meeting yesterday where a PhD student was presenting his work in microbiology, and they used triplicates. It is interesting that the same 3 seems like a magic number here, but it is not the same. Maybe I should drop a note in a few days.