Hard to tell how good Purdue is this year. They have played a tough schedule, but CMU was probably their best win so far, as they have lost to all their other tough opponents. Even in their wins, they weren't the Purdue of old - for instance they scored 61 points against a 1-7 Marist team that is giving up about 75 points per game otherwise. Still was a good win for BSU, but maybe not as good as some years.

Similarly, CMU beat Iowa State, which most years would be a huge win, but right now Iowa State has an RPI of 241, and has lost to (among others) Northern Iowa (RPI 166) and Drake (RPI 162). I don't know, maybe all the chaos swirling around Fennely the past few seasons has finally had an effect there.

Right now the top MAC teams in RPI are:
20 Buffalo
33 UT
58 BSU
66 CMU
70 WMU

WMU has played a tough schedule, but is 3-5. Of course those RPIs tend to drop as most MAC teams traditionally have weaker OOC opponents at the end of the OOC season, and then in league play the teams with real low RPIs (EMU is 270 so far, for example) pull the rest down.