recruiting analytics, linear regression
We spend so much time on college football recruiting. Ace works on it full time, and the Mathlete uses it in his models. If you don't believe how much MGoBlog readers care, check out the comments on Ace's post today.
But how far can we get with just recruiting rankings? For example, if we just had the last 4 years of Rivals recruiting data, could we predict how Michigan would do next season?
In a recent SI.com article, I used linear regression to answer this question. This method determines the linear relationship between predictor and outcome variables. For recruiting, the predictor variables are a 4 year window of team recruiting ratings while the outcome variables are the next year's team performance given by The Power Rank algorithm. This team ranking system assigns each team a rating that gives an expected margin of victory against an average team. (In 2012, Michigan had a rating of 8.7.)
The linear regression method gives a weight to each of the last 4 years of recruiting ratings. These weights imply a team rating for the next year, and these team ratings are sorted to give preseason rankings. To test this recruiting model, I compared whether these rankings or the preseason AP poll better predicted the final AP poll. (Yes, there are many problems with using the final AP poll as a measurement of team strength, but it's a starting point.)
For the last 100 teams in the preseason AP top 25, the recruiting model did as good or better on 46 of these teams. This is remarkable given the lack of information in the recruiting model. It knows nothing about winning tradition, players lost to graduation or the NFL or any number of factors used by writers who vote in the AP poll.
What About 2013?
The good news: Michigan is 9th. Hoke has recruited top 10 classes the last two years according to Rivals. This followed two classes that didn't break the top 20.
The bad news: Ohio State is 3rd. Starting in 2013 and going back, they've had the 2nd, 4th, 11th and 25th ranked classes by Rivals.
Nebraska leads the rest of the Big Ten at 20th. Notre Dame checks in at 4th with their big recruiting year.
Don't take the rankings too seriously. They consider a very limited amount of information for next season. However, they can be useful for navigating expectations.
To see the Top 25 college football teams for 2013 by recruiting rankings (which includes a link to the SI.com article), click here.