Print Page - A question about the inner workings of the RPI

Title: A question about the inner workings of the RPI
Post by: tower912 on February 04, 2007, 02:35:20 PM

As I understand the RPI, factored into the equation is the record of the teams we play as well as the record of the teams THEY play. So, by beating PU, a team that beat us, do we double dip on the RPI? The record of the previous teams that PU beat (us) improved, as well as us beating them. So, one of the teams that PU beat (us) now has a 20-4 record. It seems somewhat circular and contradictory. A little help, please.

Title: Re: A question about the inner workings of the RPI
Post by: nathanziarek on February 04, 2007, 02:50:20 PM

I think SOS works more like that.

Ken Pomroy's site has a pretty good handle on the whole RPI thing. In his judgement (and he performs his own, in his opinion better RPI calc) the basic RPI formula is this:

1/4*(Winning Percentage) + 1/2*(Opponents' Average Winning Percentage) + 1/4*(Opponents' Opponents' Winning Percentage)

So, it is a little circular, but the win and the loss essentially cancel each other out.

Ken's site is here: http://www.kenpom.com and has some great stuff on it, if you are in to numbers. He explains stuff pretty well. I tend to just sort it by RPI or Pomroy Number and look for Marquette.

Title: Re: A question about the inner workings of the RPI
Post by: nathanziarek on February 04, 2007, 10:23:23 PM

Just happened to be looking at the site, and noticed that Ken has an explanation section for the RPI:

http://kenpom.com/blog/index.php/weblog/rpi_help/

Once again, just barely english to me, but maybe it helps you out.

Title: Re: A question about the inner workings of the RPI
Post by: spartan3186 on February 04, 2007, 11:05:19 PM

Part II (50%): Average opponents' winning percentage. To calculate this, you must calculate each opponent's winning percentage individually and average those figures. This is NOT calculated from the opponents' combined record. Games involving the team for whom we are calculating the RPI are ignored

PS Its Providence College not Providence University... a lot of people seem to make that mistake

Title: Re: A question about the inner workings of the RPI
Post by: nathanziarek on February 04, 2007, 11:24:04 PM

See...I didn't even read that far.

I was going to come up with the math to figur out if the numbers did actually cancel each other out, but that started seming tedious just after looking at our opponents winning percentage. Really glad I didn't now :)

As for PC v PU ... One just has a better ring to it, doesn't it? :)

Title: Re: A question about the inner workings of the RPI
Post by: muwarrior87 on February 05, 2007, 04:02:36 PM

quick question...what is the basic difference btwn RPI and SOS...shouldn't these go hand in hand in most cases? i was looking on CBS and some teams w/ higher RPI's have really weak SOS's, Florida is a pretty good example...if anyone can clarify this, it'd be much appreciated :)

Title: Re: A question about the inner workings of the RPI
Post by: dwaderoy2004 on February 05, 2007, 04:25:16 PM

the sos is basically the rpi formula without taking your winning percentage into effect...

Title: Re: A question about the inner workings of the RPI
Post by: muwarrior87 on February 05, 2007, 04:39:47 PM

ok, thanks :)

MUScoop

MUScoop => Hangin' at the Al => Topic started by: tower912 on February 04, 2007, 02:35:20 PM