Why RPI Matters

For several years I have been trying to educate you all on the importance of three little letters, in baseball, OPS. I think succeeded so now I will move on to college basketball where the three crucial letters are RPI.
Later today the brackets will be announced and RPI will be used to justify why teams got in or got left out.
RPI is simply a formula based on your winning percentage, your opponents' winning percentage and your opponents' opponents' winning percentage. With 345 teams playing such disparate schedules, RPI helps compare teams with vastly different records and vastly different schedule strengths.

Note: there are major flaws in the SOS (strength of schedule) numbers making them somewhat unreliable. For instance, if one team were to play #1 and #345 in RPI and another team played say, #50 and #51, the team that played #1 would still have a weaker schedule. Though the odds of going 2-0 against that pair are much lower. Maybe I will expand on the flaws of SOS another time.

Let me give you an example of what RPI can tell us:
On Christmas Day Tulane was 9-2 and Long Beach State was 5-6. Tulane's SOS was 342 (even though they had played #1 Syracuse) and Long Beach State's SOS was 1.
Tulane's RPI was roughly 150 and Long Beach was 10 or 11 (wish I had recorded these numbers that day.)
Old school basketball watchers and the idiots who vote in the polls might say clearly a team with 9 wins ins better than a team with 5. No way can they be 140 spots better.
But Tulane wins were against teams like Navy, Maryland Eastern Shore, Alabama A&M and Alcorn State. All of which have RPIs (final numbers) higher than 300.
Compare that to Long Beach State which lost to San Diego St, Louisville, Kansas, North Carolina and Kansas State. All of those are in the top 50, 4 in the top 25.
But RPI is not just useful for what it tells us about the past, it also predicts the future.
After the 5-6 start LBSU went 19-2, with one of the losses against another top 25 team, Creighton.



Meanwhile, Tulane went 4-14 after that hot start.
So maybe it was predictable that Tulane would end the season with an RPI of 249, while Long Beach State finished 39th, got a 12 seed in the tournament with a decent chance to upset New Mexico in the first round.