College Football Bowl Game Model

I made model to predict the outcome of NCAA football bowl games. My model is based only on the outcome of regular season games, and is an ensemble of two simple mathematical models.

Random Walk Model

The first is a random walk model (i.e. Google Page Rank). The idea of the random walk model is to imagine a network where each node (point) represents a team. There is a one-way edge between two teams if they played a game, and the direction of the path points toward the winning team. Assume you begin the walk at a random node and begin travelling along the edges randomly. A team's ranking is the probability that you are located at that team's node after a very long time. The idea of the Google Page Rank algorithm is that if you add a little more randomness -- a small probability of moving from any node to any other node -- then this limiting probability is well determined.

I weight the graph's edges by the score differential. I tried applying various functions to the score differential as well as the score differential scaled by the winning team's score. An idiosyncrasy of the random walk model is that it rewards teams that beat other teams with very few losses, even when that team had mediocre results through the season. To compensate for this quirk, I used a large Google constant, that is I made the small probability of moving from any node to any other node quite a bit larger than the default value.

Regression Model

The second is a regression model where each game is an observation. The teams participating in the game are the features, and I arbitrarily assign one team to be team one and the other to be team two. The value of team one is +1 and the value of team two is -1 for each game. The difference in score (team one score less team two score) is the label. One advantage of the regression model is that it was very simple to do model selection using cross-validation. I used L2 regularization and determined the amount of regularization through cross-validation.


Model Prediction
Virginia Tech 55 Tulsa 52 Virginia Tech
Nebraska 37 UCLA 29 Nebraska
Navy 44 Pittsburgh 28 Navy
Minnesota 21 Central Michigan 14 Central Michigan
California 55 Air Force 36 California
Baylor 49 North Carolina 38 North Carolina
Nevada 28 Colorado State 23 Colorado State
LSU 56 Texas Tech 27 LSU
Auburn 31 Memphis 10 Memphis
Mississippi State 51 NC State 28 Mississippi State
Louisville 27 Texas A&M 21 Texas A&M
Wisconsin 23 USC 21 USC
Houston 38 Florida State 24 Florida State
Clemson 37 Oklahoma 17 Clemson
Alabama 38 Michigan State 0 Michigan State
Tennessee 45 Northwestern 6 Northwestern
Michigan 41 Florida 7 Michigan
Ohio State 44 Notre Dame 28 Ohio State
(6) Stanford 45 (5) Iowa 16 Stanford
(12) Ole Miss 48 (16) Oklahoma State 20 Ole Miss
Georgia 24 Penn State 17 Georgia
Arkansas 45 Kansas State 23 Arkansas
(11) TCU 47 (15) Oregon 41 (3OT) TCU
West Virginia 43 Arizona State 42 West Virginia
(2) Alabama 45 (1) Clemson 40 Clemson


Click here to see the code for my model.