http://www.grantland.com/story/_/id/...best-nfl-stats
Football's Pythagorean Theorem
In a Sentence: Point differential is a better indicator of future winning percentage than winning percentage itself.
How It Works: Created by Bill James for baseball and modified for football in the early '90s by current Houston Rockets general manager Daryl Morey, the Pythagorean theorem (or "Pythagorean expectation") is a formula that translates a team's points scored and allowed into an "expected" winning percentage. That formula isn't exactly for the faint of heart:
Points For2.37 / (Points For2.37 + Points Against2.37)
As an example, let's take the 2011 Chiefs, who went 7-9 while scoring 212 points and allowing 338. Our formula is 2122.37 / (2122.37 + 3382.37) = 0.248. That's the Chiefs' expected winning percentage from their point differential, and if we multiply it by 16 games, we get a total of just 4.0 wins. The Pythagorean theorem suggests that the Chiefs outperformed their true level of performance by three full wins.
See we did better last year.
