How do you calculate %xHKO?

I thought that your damage range was calculated first, defense subtracted and all, and then the random was chosen.

One could, of course, do a study of some sort on damage distributions, but it'd be tedious and/or not reveal much.

pretty sure that since we dont do damage in increments of 2-11 (depending on skills used) instead of 1 that everything gets applied before taking the random.
with a damage range of 160~300 powerstrike can dish out both 599 and 600 on [certain monsters] no problem. i dont think you can find a clearer revelation.