Random Walker Ranking for NCAA Division I-A Football
Abstract
Each December, college football fans and pundits across America debate which two teams should meet in the NCAA Division I-A National Championship game. The Bowl Championship Series (BCS) standings employed to select the teams invited to this game are intended to provide an unequivocal #1 v. #2 game for the championship; however, this selection process has itself been highly controversial in recent years. The computer algorithms that constitute one part of the BCS standings often act as lightning rods for the controversy, in part because they are inadequately explained to the public. We present an alternative algorithm that is simply explained yet remains effective at ranking the best teams. We define a ranking in terms of biased random walkers on the graph formed by the schedule of games played, with two teams (vertices) connected by an edge if they played each other. Each random walker moves from team to team by selecting a game and "voting" for its winner with probability p, tracing out a never-ending path motivated by the "my team beat your team" argument. We study the statistical properties of a collection of such walkers, relate the rankings to the community structure of the underlying network, and demonstrate the results for recent NCAA Division I-A seasons. We also discuss the algorithm's asymptotic behavior, illustrated with some analytically tractable cases for round-robin tournaments, and discuss possible generalizations.
Keywords
Cite
@article{arxiv.physics/0310148,
title = {Random Walker Ranking for NCAA Division I-A Football},
author = {Thomas Callaghan and Peter J. Mucha and Mason A. Porter},
journal= {arXiv preprint arXiv:physics/0310148},
year = {2012}
}
Comments
26 pages, 5 figures totalling 7 images. Commentary available online, with 2003-2006 rankings (http://rankings.amath.unc.edu). Second version rescales some images, adds a reference and cleans up some grammar. Third version adds results, while reorganizing and slightly shortening manuscript. Fourth and final version (accepted and marked up, to appear in Am. Math. Monthly) clarifies a few points from the review process and fixes grammatical markups