Wednesday, September 14, 2016

Who's gaming the RPI this year?

Among the RPI's well-known flaws is that it can be easily gamed. As Luke Winn explained several years ago:
Seventy-five percent of the RPI formula is about strength of schedule (SOS), and because the RPI uses the flawed metric of raw winning percentage to assess SOS, it fails to provide a true measure of the quality of opponents. The truest measure available is's NCSOS ranking, which creates a pythagorean winning percentage based on opponents' adjusted efficiency, and even adjusts for home/neutral/road situations, which the SOS portion of RPI does not.
So in the RPI, your schedule is essentially your destiny. To show this, I set up a hypothetical bubble team (with a pythag of .8000 on a neutral court) and ran the RPI for that team playing every team's announced 2016-17 schedule. Obviously, this excludes later rounds of holiday tournaments and unannounced games, but these have just minor effects at this point.

The results are available the T-Rank bubble-rpi page. About half the schedules produce a bubble-team rank between 40-60, which is what you'd expect since the hypothetical bubble team in question would be around #50 in the T-Rank. So bubble-rpi rank around 50 shows that a team's current schedule is reasonably neutral for RPI purposes.

The team with the "best" schedule for maximizing the RPI of a bubble team is North Carolina's. A bubble team playing North Carolina's announced schedule (notably missing two rounds in Maui, including a possible game against Wisconsin), would be expected to go 17-12 and rank 16th in the RPI. Would that be enough to get into the tournament? Assuming those 17 wins include a number of top 50 conquests, I think so. It compares to what Oregon State did last year: 18-12 on Selection Sunday with an RPI rank of 33 and a number of "good wins" got them a 7-seed (!) despite a Kenpom / T-Rank around 60th.

That said, a schedule like North Carolina's is probably not the most advisable for a true bubble team, because it comes to its high ranking rather honestly: by playing a lot of tough games. Sure, the average bubble team would win 17 games, but a bubble team that got a few bad bounces could easily miss the NIT with that schedule.

The schedule with the best mix of good projected record and good projected RPI rank is probably Rhode Island's. A bubble team playing Rhode Island's schedule would project to 21-8 with an RPI rank of 18 -- pretty much a sure thing for the tournament. Rhode Island will also play either Duke or Penn St. in their preseason tournament, in which case the projected RPI rank changes to 17 or 20, respectively. In any case, a bubble team playing that schedule is looking at very likely at least 19 regular season wins and a top 20 RPI. Well done Rams!

How did they do it? The old-fashioned way: lots of beatable mid-majors, and no worthless sub-250 cupcakes. The only downside of their schedule is that it doesn't provide a lot of opportunity for resume-building top-50 wins, and that's why T-Rank currently projects the Rams among the last 4 teams into the tournament (FWIW).

On the flip side, the schedule with the absolute worst RPI profile belongs to North Carolina Central out of the MEAC. A bubble team playing that schedule would be expected to go 22-3 but rank 128th in the RPI. The big problem for NC Central is the MEAC: it has no good teams, and they're all going to get ground to dust in the non-conference.

But of course no potential bubble team plays a schedule like NC Central's, so let's look instead at the worst RPI schedules among high major teams that might have designs on a tournament berth. In that cohort, there are really just four teams that have unusually unfavorable schedules:

Texas Tech rather famously gamed the RPI last year, but Tubby's successor will have a much less favorable slate this year. Their non-conference schedule includes a pathetic seven games against sub-250 projected teams, plus #232 North Texas.  That said, they benefit from playing in the Big 12, which projects to be strong top to bottom, so even if they are a bubble-quality team this year (and T-Rank thinks they'll be slightly better than that) they should pick up enough quality wins in conference play to neutralize the stigma of a low raw RPI rank.

Two teams that could suffer from their unfavorable schedules are Utah and Northwestern. Of Utah's eight D-I scheduled non-conference games, six are of the RPI-killing cupcake variety. Throw in Utah's two games against non-DI teams (which don't count for RPI) and 80% of Utah's scheduled non-conference is garbage. Utah does have two games TBD in the Diamond Head Classic, and if they play Illinois St. and San Diego St. that would lift the bubble-projected RPI to 58th. But they've got probably an equal chance of playing Hawaii and Tulsa, which would change the projection back to 68th. Given that Utah could well be a bubble team this year, this schedule could do them in.

Northwestern is less likely to be a bubble-quality team, but if it is its schedule could be a limiting factor. Northwestern also plays six RPI-killing cupcakes. Even more respectable opponents like DePaul and Wake Forest are probably a negative, because those are major conference doormats likely to end up with a bad record -- but they're also very capable of pulling an upset. So it's taking a risk of a loss without any SOS bump.

Ultimately, this exercise illustrates the most damning thing about the RPI: a hypothetical bubble team could finish anywhere between 16th and 128th, completely dependent on its schedule. In other words, the RPI is primarily a metric that measures schedule quality, not team quality.

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