Friday, March 6, 2009

And Now You Know!: RPI

What in the world does RPI mean and why am I hearing about it so much? Plain and simple it is a ratings percentage index used by the NCAA to rank it's basketball teams. Here is the formula:

¼(Win %) + ½(Opponents' Avg. Win %) + ¼(Opponents' Opponents' Win %)

The other part of this formula is to multiply the win % by another variable depending on whether the game was played at home, on the road, or a neutral site. It's not nearly as difficult as the Quarterback Rating Formula or trying to understand the BCS calculations, but it requires a lot of numbers to figure out.

The bracket was established in 1981 to help the Selection Committee find the best teams for the tournament. So with that said, shouldn't selecting the top 65 teams be easy considering they are all ranked?

You might think so, even after the automatic bids are selected, but that isn't the case. I took data from the past 10 years and here are some of the trends that I found.

-On average, of the top 65 RPI teams, 51 of them get into the tournament. This seems reasonable considering there are automatic bids given to weaker teams such as the Patriot League, Northeast Conference, and Southwestern Athletic Conference.

-The at large process takes in many factors such as conference strength and last 10 games going into the tournament. In 1999 when New Mexico was selected as an at large team. Their last 10 games they went 7-3, which included playing 4 neutral site games and 3 road games. That year 21 other teams were overlooked ahead of them int he RPI that did not make the tournament. New Mexico was a No. 9 in the tournament and won their first game before bowing out to UConn in the second round. Oregon that year had an RPI of 40 and missed out on the Big Dance.

-It isn't understood why Oregon missed out that year or why any team gets in with a lower RPI than another team that misses out Although in 2003 the team with the 5th highest RPI missed the tournament. Georgia was under NCAA probation for recruiting infractions and elected to forgo any post season tournament in lieu of other repercussions. Aside from Georgia it was in 2006 when 21st ranked Missouri State got left out of the tournament and was the highest ranked RPI team to be looked over by the committee. Before you claim that the Missouri Valley Conference should have got more than just the automatic bid note that in 2006 the MVC had four other teams that made the tournament. Why not five?

Things like this happen each and every year. Teams are snubbed and then the question arises as to whether or not the field should be expanded. Well the answer to that question is unequivocally, no. Did it matter if Oregon missed the tournament in 1999 but in 2008 they were the last at large team to get in? 1% of the top 32 teams over the past decade have missed the tournament (Dayton 2008, Air Force 2007, Missouri St & Hofstra 2006).

There is no exact science when figuring out who the best teams are, although the RPI would suggest that there is a science for determining the best teams? There is no method to the madness by the selection committee. I couldn't say that teams with a bear mascot are picked more often than creatures that walk or swim, or teams in the central time zone get in more often than those from the mountain time zone. It all comes down to how the committee is feeling that day.

I look at a lot of stats and after doing regression analysis and looking for the coefficients, sometimes you just have to throw your hands up and suggest that randomness happens. But, what happens before the tournament is different than what happens during the tournament.

And Now You Know! (And Knowing is Half the Battle)

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Craig said...

I think the stat regarding the teams in the top 32 rpi not making the tournament is very telling -- all those teams are mid majors. It seems indicative of the way the committee is handling at large bids recently; that is, they go to power conference teams. It wasn't but 3 years ago and we were celebrating a mid major reaching the final four, and this year we're looking at 4 mid major at large bids (and there would have been two had Butler or Dayon or Xavier won their conference tournaments)