Sunday, November 16, 2014

Who Should Make The Playoffs? (feat. SORTACUS)

It's now been over two years since I made a blog post, but the process behind the college football playoff selection was too much for me to resist.  Does Ohio State deserve a shot?  Is the SEC overrated (or underrated)?  Should we be talking about Marshall?  I brushed off an old skill set in an attempt to answer these questions and more.

College Football Playoffs

I have long had a fascination with the process used to select college football's champion.  It a sport uniquely unsuited for a large playoff bracket, the kind the selects appropriate champions in the NBA, or creates a month of excitement in college basketball.  I wrote about my philosophy on NCAA football champions extensively a few years ago during what I termed BCS Week

For now I'll skip the details on who deserves to be in the playoffs, and instead hit upon the main points here.

-Championships, and therefore playoffs, should reward performance, not potential.  Luck happens in sports, and sometimes Northwestern beats Notre Dame.  The only goal in a game is to win, and playoff selection should reflect that.

-Not all wins are equal.  In other sports nothing besides record determines seeding, but with the disparity in college football that is often unreasonable.

-There should be an algorithm for determining qualifiers.  This is true in most other sports, the algorithm is just wins and tie breakers.  A committee of people, all with ties to teams, has inherent biases a computer doesn't.  Coming up with an algorithm is a challenge.  Fortunately, I have a proposal.


SORTACUS is a computer ranking system that I created with Andy Meisner to rate items based off head to head comparisons.  It's currently used only to rank Andy's 100 favorite movies, and occasionally help my family select where to go to dinner.  Because games are just head-to-head comparisons however, it is easily applied to college football.

If these posts continue I'll describe the algorithm in detail at some point, but a summary will have to satisfy the math nerds for now.  It uses Bayesian theory to adjust the odds that a team has any given rating.  Each game is another observation to adjust the probability that team A has rating X.  It's fun and exciting math, if you're into that sort of thing.  For now though, I'll post a few summary points.

-Only wins and losses matter.  Margin of victory is ignored.  This makes the ratings worse at predicting future results, but better determining the most deserving playoff qualifiers.  If you want predictions and projections, check out my work for TeamRankings.

-Home and away are not implemented currently.  I think it would be reasonable to adjust and include a game's locations, it would just require some additions to the code.

-Only games against FBS teams matter.  A loss to Northern Iowa would slip through the cracks (for now).

-A win never hurts a team.  Many ratings systems include average opponent strength in some way.  A win against a bad team could hurt a good team, even if it was a lopsided game.  With SORTACUS, even a win against a junior high team can't hurt.

Top 25

The experienced readers likely just jumped straight to these ratings.  Below is the SORTACUS top 25 using games through Saturday.  In theory, the top 4 teams are the most worthy of a playoff spot so far.

Rank Team Record Rating
1  Florida St 9-0 22.62
2  Alabama 9-1 21.90
3  Mississippi St 8-1 20.39
4  Oregon 8-1 19.95
5  TCU 8-1 19.26
6  Mississippi 7-2 17.49
7  Ohio St 9-1 17.41
8  UCLA 8-2 16.68
9  Marshall 9-0 16.29
10  Baylor 7-1 16.20
11  Auburn 7-3 15.63
12  Georgia 8-2 14.38
13  Colorado St 8-1 14.36
14  Arizona 8-2 14.06
15  Michigan St 7-2 13.70
16  Kansas St 6-2 13.70
17  Boise St 8-2 13.44
18  Arizona St 7-2 12.90
19  Oklahoma 7-3 12.72
20  Georgia Tech 8-2 12.53
21  Nebraska 7-2 11.90
22  Missouri 7-2 11.23
23  Wisconsin 7-2 11.20
24  Louisiana Tech 7-2 10.53
25  LSU 6-4 10.46

Through Novermber 16 the playoffs should contain Florida State, Alabama, Mississippi State, and Oregon with TCU on the outside looking in.  The playoff rankings this week may actually agree with that, which is a good check for both SORTACUS and the committee.

What else stands out here?

The Big Ten is probably being overrated by the committee.  Ohio State is probably worthy of a fair shot at the playoffs, but Michigan State, Nebraska, and Wisconsin don't fare well with SORTACUS.

The SEC is as good as midseason polls said.  Schools in the West have beaten up on each other, potentially jeopardizing an SEC spot in the playoff.  SORTACUS puts five teams in the top twelve though, almost guaranteeing at least one deserves a final spot.

Marshall is number nine?  That seems high and probably is.  There aren't enough inter-conference data points for SORTACUS to work with.  Still, for Marshall to be undefeated but not among the 25 most deserving playoff teams is a silly mistake on the committee's part.

How is my team doing?

Schools I'm associated with don't show up in the top 25.  Here's where a few notable ones land:
Maryland:  41st, rating of 5.18
Iowa:  49, 3.51
Stanford:  55, 1.96
Northwestern:  68, -0.26
Iowa State:  85, -4.92
Purdue:  91, -6.15
New Mexico:  106, -10.68

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