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Friday, June 08, 2007

SDPI - Another Interesting Statistical Variable

In my continuing quest to continue to help bring college football into the Moneyball era I've run across another interesting football statistic. This one comes to you from the fine work of Statistically Speaking.

This variable is the Standard Deviation Power Index. This index originates from Eddie Epstein’s book Dominance. It focuses solely on conference play and looks at a team's points scored and allowed relative to the league average and standard deviation.

Statistically Speaking later provides an example of how SDPI is calculated:
The mean points scored and allowed for all ACC teams in conference play (championship game not included) was 162 points. The standard deviation for points scored was 35.97. The standard deviation for points allowed was 51.18. Coastal Division champ Georgia Tech scored 213 and allowed 155 points. Georgia Tech’s offensive SDPI was 1.42 = ([213-162]/35.97). Their defensive SDPI was .14 = ([162-155]/51.18). Their total SDPI was 1.55 (not 1.56 because the other two were rounded). In the 2006 ACC, that was good for third best.
As part of his SDPI project, Statistically Speaking broke down the conferences in a historical manner. He examined the Big 12 from 1998-2006. This is what Nebraska's SDPI looks like in graphical form for those particular years.

This is what he had to say about Nebraska's historical SDPI in the Big 12.
Frank Solich kept the Huskers near the top of the college football world (though not quite the heights reached under Tom Osborne) for four seasons. The wheels came off in 2002, but Solich seemed to reverse the teams trajectory in 2003 before being fired despite a 10-3 record. Bill Callahan took over in 2005 and promptly guided the Huskers to their first losing season since 1961. The Huskers improved and were an average team in 2005. They improved yet again in 2006 and may be on their way to recovering their place in the Big 12 pecking order.

First Place SDPI Finishes: 2000
You'll first want to keep in mind, the SDPI does not adjust for schedule strength for conferences such as the Big 12 where each team does not play each other and it ignores special teams which can play a significant role in both points scored and points allowed. However, this seems again like an interesting statistic that appears to correlate with performance at least to some degree.

I just wanted to introduce it to you today. I plan on getting into at a deeper level in the future.