RPI vs. the “Eyeball Test”

How much of a role does RPI play when determining post season seeding? Photo by: Mervyn Chua

Over the years, the Ratings Percentage Index, or RPI, has become a fixture within the college basketball landscape.  For those of you who are unfamiliar, the RPI is basically a formula that assigns points based off of a given team’s wins, losses, and strength of schedule.  Created back in 1981, the primary function of the Index (at least in my opinion) has always been its ability to stack up one team’s resume against another for the purpose of evaluating who is more deserving of a potential postseason seed/bid.  And whereas the index does fulfill a primary purpose, it is by no means flawless.

Those of us who watch college basketball frequently know all too well that the RPI system usually contradicts how we assess a particular team versus another.  Often referred to as the “eyeball test”, most fans garner their own opinions as to where they feel a specific team belongs in relation to competing programs across the nation.  For example, last week I could watch an Indiana Hoosiers team lose on the road vs. Minnesota, while a New Mexico Lobos team beats San Diego State at home.  After watching both teams on a regular basis this season, I feel confident that the Hoosiers would beat the Lobos on a neutral floor.  Yet, the current RPI ranking has the Lobos (.6685) ahead of the Hoosiers (.6451).

The basic formula of the RPI is rather simplistic, but does in fact make sense (well, on most occasions it does).  The formula is as follows:

• 25% team winning percentage (WP)
• 50% opponents’ average winning percentage (OWP)
• 25% opponents’ opponents average winning percentage (OOWP).

Back in 2004, the formula was slightly modified to give more weight to road wins (now worth 1.4), as opposed to home wins (now worth 0.6).  The thought process here was that statistical data over the years had shown that the home team was winning at around a 66% rate.  This modification certainly made sense to me, as winning on the road in college basketball (especially conference games) is no easy task.  For example, yesterdays huge road upset by Purdue (vs. Wisconsin) at the Kohl Center is more valuable within the current ratings system then their previous home win versus Northwestern back on February 24^th.  Makes sense, right?

What probably isn’t going to make sense to some of you (maybe all) is the current RPI Top 50.  I know there are some glaring discrepancies that stand out to me when I look at the list.

For the sake of argument, here is the current Top 50 RPI teams in the nation:

It’s hard to envision a scenario where the Arizona Wildcats should be ranked ahead of the UCLA Bruins right now. Photo by: Neon Tommy

Also for the sake of argument, here are some general observations/questions regarding how some of these teams matchup outside the realm of the RPI (via the Eye Ball test):

• The North Carolina Tar Heels currently have an RPI rating of 19.  And although they have been playing better basketball of late, they currently possess zero Top 25 wins, and are a combined 2-11 vs. the RPI Top 50.  They have one meaningful non-conference win to their name (UNLV), and a just as equally bad non-conference loss (Texas).  Illinois currently has an RPI of 30.  They have four Top 25 wins (9 Top 50), including victories over Butler and Indiana (two teams that beat UNC).  As of today, it is hard to fathom a scenario where the Tar Heels have a more credible resume than the Fighting Illini.  According to the RPI, they do.
• With a current RPI of 21, the Memphis Tigers have dominated Conference USA to the tune of 14 wins and 0 losses.  That is impressive until you consider that Conference USA is currently the 11^th ranked RPI conference nationally.  It is true that the Tigers scheduled impressive non-conference games versus VCU, Minnesota, and Louisville.  It is also true that they lost every one of those games.  They currently possess just two Top 50 wins, and recently lost to a middle of the pack Xavier team last Tuesday.  The Saint Louis Billikens are the 29^th ranked RPI team, yet their overall body of work trumps the Tigers immensely.  Consider this, the Billikens currently possess an impressive 7-3 mark versus the RPI Top 50 (including 3 Top 25 wins).  They have not lost a game since January 23^rd, and dismantled the same VCU team that beat the Tigers.  Once again, common sense tells us that the Billikens are the stronger team.
• I’ll keep this one short.  The Arizona Wildcats currently have an RPI rating of 13.  They have some excellent non-conference wins over Florida, Miami, and San Diego State.  Yet, they currently find themselves looking up at the Pac 12 leading UCLA Bruins (tied with Oregon).  UCLA has defeated the Wildcats in both of their meetings this year, yet have a current RPI of 32.  The Bruins are winners of 4 in a row.  The Wildcats have lost 4 of their last 8.  Who you got?

I could probably go on and nitpick about the current RPI ratings, but you get the picture. Listen, the objective of this post isn’t to dispel the current RPI setup.  As I stated above, I do believe that it serves a purpose within today’s game.  However, I do think we sometimes get lost in the repetitive calculations that are spit out at us on a regular basis.  At the end of the day, we are lucky enough to witness a college basketball tournament that determines an overall winner.  Still, I just hope the Selection Committee is using the “eyeball test” in a comparable fashion to the RPI system a couple weeks from now.

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