Thursday, January 8, 2009

A Scoring Efficiency Model And The Playoffs

by Cyril Smith

This is the time of year when the NFL really gets interesting.  The ups and downs of the regular season have ended and the playoffs hold the promise of competitive matchups for every game.  I have put together a simple scoring efficiency model for predicting the outcome of playoff games.  I look at the ability of a team to score based on its time of possession, in other words points per minute (ppm). PPM measures not only offense but defense and special teams as well.  Both good defenses and good special teams give the offense good field position, which means less time is needed to score.  A defensive touchdown or a kick return for a touchdown represents scoring with minimal time expenditure.

The model takes the average points per minute for the last nine games.  Each playoff team's ppm is calculated by dividing its aggregate nine game score by its aggregate nine game time of possession.  An assumption of the model is that the playoff teams are roughly equal; accordingly each team's basic score is calculated by multiplying its average ppm by 30. I then make three adjustments: home team gets 3 points; a team whose quarterback has never started a playoff game is docked 3 points; and a team whose average ppm has increased significantly over the past three games compared to games four through six is given 3 points for trend.

How did the model do on the first round of playoffs? It had Arizona over Atlanta by 6 points; San Diego over Indianapolis by 3 points; Miami over Baltimore by 1 point; and Philadelphia over Minnesota by 1 point.

For next weekend the model has Carolina over Arizona by 11; San Diego over Pittsburgh by 4; Tennessee over Baltimore by 3 1/2; and New York over Philadelphia by 4 1/2.

Anonymous said...

that's pretty cool. I was going to suggest points-per-play might be more meaningful than points-per-minute. But points-per-minute is WAY easier to calculate with, and probably almost as accurate, so I understand. A modification you may (or may not) want to consider is that HFA in the NFL is almost exactly 2.5 points, not 3.

Josh said...

the model has Carolina over Arizona by 11; San Diego over Pittsburgh by 4; Tennessee over Baltimore by 3 1/2; and New York over Philadelphia by 4 1/2.

Whoops.

Brian Burke said...

Hey, those results surprised everyone.