College Football Playoff = AP poll + RPI

A few weeks ago the College Football Playoff (CFP) committee published their first rankings.  That led to this train of though:

  • Wow.  Those look a lot like the AP rankings.
  • I wonder what rankings the CFP is closest too?
  • Where can I get a bunch of different ratings to compere?  MASSEY!

So, I downloaded all of the ratings that Massey had collected and compared each of them to the CFP rankings using Kendall’s Tau.  And guess what?  The AP rankings are the most highly correlated rankings with the CFP with tau=.8478261.  So basically, we’re back to the days when the AP picked the national champion?  Well not exactly.  Now we have the AP AND the RPI.  Because guess what’s next most highly correlated? Real Time RPI!  At tau=.833333333333, the RPI falls just behind the AP in the most highly correlated rankings. This is rather alarming, because basically anyone who has any idea what they are doing, knows the RPI is terrible.  (See this, this, and this.)  To highlight this, I’ll take a quote from that second link from Nate Silver in regards to the RPI in terms of selecting NCAA basketball teams:

Over the long run, R.P.I. has predicted the outcome of N.C.A.A. games more poorly than almost any other system.

Basically, the RPI is terrible, everyone who knows what they are doing knows it, but it still gets used because….I have no idea.

Following the RPI, you have the USA Today Coaches poll with a tau of .8115942.  So basically the CFP is using some sort of secret combination of two human polls and basically the worst non-human ranking that is available.  As opposed to the BCS which was a known combination of two human polls and 6 computer systems that ranged from very good to dreadful.  (At least the BCS didn’t involve completely inexplicable people like Condoleezza Rice.  Seriously, why is she involved in this?  If you really want a woman on the committee aren’t there literally thousands of women more qualified for this than her?)

Also, for the sake of it, I made a decision tree to try to predict the CFB rankings.  It looks like the formula for getting into the playoff is be top 15 in coaches poll and then be top 3 in RPI.   The three variables are the USA Today coaches poll (X.USA), the AP poll (X.AP), and Real Time RPI (X.RTR).  My response was the CFP rank with all teams not ranked set to 26.



All of this of course would infuriate me if the NCAA was earnestly trying to find the 4 best teams in college football to put into a playoff.  But I suspect that’s not necessarily their goal.  The NCAA is about one thing: MONEY.  They can say whatever they want, but they are ruled by money (none of which goes to the actual people who produce the product!).  Because of this, this sham process somehow bothers me less.  The NCAA is trying to get the 4 “best” teams into the college football playoff.  They are just using their definition of best, which is probably much different than that of the average fan.  And besides I’ve got bigger problems with the NCAA. (See here, here, here, here, here, and here for starters.)



Posted on November 12, 2014, in Uncategorized. Bookmark the permalink. Leave a comment.

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