Sunday, October 7, 2012

College Football Rankings - Week 7

The 1892 Alabama Football Team
When men were men and hats were hats
Here is my first attempt at creating a betting market power ranking for College Football.  The goal here is to try to reverse engineer an implied power ranking from the point spreads set by Vegas and the offshore sportsbooks.  In a nutshell, I'm trying to figure out what the betting public "thinks".  See my Methodology page for a simple example of how the rankings work (also see here for a detailed NFL example).

Here are some details on the methodology:
  • Home field advantage is assumed to be worth 3.5 points (I derived this from 5 seasons worth of point spreads)
  • Recent games are weighted more than games played early in the season.  The weight used is as follows: weight = 1/(2.8 + days), where days is how many days ago the game in question was.
  • The key output is GPF, which stands for Generic Points Favored.  It's what you would expect the team to be favored by against a Division 1A average opponent at a neutral site.
I don't follow college football too closely, so I included the AP and Coaches Polls in the table below as a point of comparison and a reality check for myself.  I'm also just showing the top 56 Division 1A teams here (the cutoff chosen to include all ranked teams).  If you want the full list, you can find them at this Google Docs Spreadsheet (poor Gardner Webb).

By necessity, NCAA football polls are less about predicting future success as they are about rewarding past wins.  Vegas has no need nor inclination to be fair to teams. They care only about the future.  Where you see differences in these rankings and the polls, they are most likely driven by record.


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