In reading through this thread, it seems like part of the debate is driven by the fact that there is little commonality on which to calculate a meaningful "average". There's average by Purdue's own standards, there's average by 351 D1 teams, there's average by B1G, and probably more. And I think some people are getting way to hung up on the literal definition of the word anyway.
This argument, to me, is really more about how Purdue has performed against it's peers, which admittedly, creates then a new (and also potentially subjective) question as to who its peers are. Given that Purdue plays in a conference that is normally one of the better basketball conferences in the NCAA, performance in the B1G is probably a fair place from which to start - which I think is probably the viewpoint that
@*4purdue* and
@icewind7 where taking. I'd go a step further and broaden the peer group to other basketball conferences - ACC being a good example; football stinks there. Heck, maybe it should be all 5 power conferences, just because some are split between being - generally speaking - good at football vs. good at basketball.
So let's say you went that route of power 5 as your starting point. Next, you eliminate programs that during the period in question, which I think most would agree on 10 years; not only a nice round number, but excludes Painter's 1st year, which is probably fair. Then, you should probably exclude programs who have been total losers over that period, i.e. the Rutgers of the world. Rutgers, Wake Forest, Penn State... these are not Purdue's peers. Purdue has won 22 B1G championships for crying out loud! I don't know where exactly you draw the line, but you'd have to at least give consideration to removing teams in the bottom 10% (maybe 20%?) of conference records during that time. Just like it isn't really fair to compare Painter/Purdue to Calipari/Kentucky to argue Purdue's failures, it's equally stupid to include the bottom feeders in any debate about how Purdue measures up against its peers.
Lastly, one would probably want to also add in teams outside the power 5 that have been reasonably good programs over the last decade. BYU, Wichita St., Gonzaga, Butler, etc. I suppose you might also have to consider removing a team or two at the top if they are so dominant for which comparing Purdue isn't fair - UK is the obvious example as their recruiting puts them in a league of their own with Cal. But, what about Duke? Kansas? Or maybe it's ok to keep them in because the cut-off on the bottom is going to include just some OK teams anyway, so perhaps it balances out. But only once you have a reasonable peer group defined can you truly assess Purdue's/Painter's performance.
EDIT: After having finished writing this, I really wish I had time to do exactly what I described, but maybe somebody else will take on that adventure.
