Friday, September 6, 2013

CFL Pythagorean Wins


I'm a big believer in statistics and analysis when it comes to sports.  As noted by some on /r/cfl previously, there is a significant lack of advanced stats for the CFL.  I'm not a statistician, nor do I have charting stats for each any every game like the NFL stats sites, so there are definite limits on what I can provide, but one stat I can calculate easily is Pythagorean Wins.

Bill James created the formula for baseball years ago, and it's been modified to better suit the NFL since then.  Obviously the CFL is not the CFL, but the season is of similar length and scoring numbers are also in the same ball park, so I believe the stat should apply fairly well to our league.  Down the line I will look at some past seasons and see if I can determine how well (or poorly) it actually does work.

The formula itself is based on the idea that not all wins are created equal, and that point differential is actually a better indicator of future winning percentage than actual wins and losses.  When applied to NFL games, the stat is a good indicator of future performance, both for future seasons, and second halves of the same season.

For a more detailed explanation from someone much smarter than I, check out Bill Barnwell's explanation on grantland.com.

With all of that said, we are at the half way point of the CFL season, so this is a perfect time to run the numbers on the first half and see what they might tell us.

Legend
P-W%: Pythagorean Winning Percentage, P-W: Pythagorean Wins, P W-L: Pythagorean Win-Loss,
Diff: Difference between Py Wins and Actual wins, P-W-T: Pythagorean Win Total (projected over 18 games)
 

By the numbers, Saskatchewan and BC are the luckiest teams of the first half, while Edmonton and Winnipeg are the unluckiest.  Despite being the luckiest team, the formula still believes that the Riders are the best team in the league, while Edmonton has been particularly unlucky, performing almost 2.5 wins below expectation. 

Teams which over or under perform the formula by a wide margin tend to fall back or climb closer to their expected win total as the season progresses, so according to Pythagoras, both Edmonton and Winnipeg fans should have some hope that their team will rebound slightly in the second half.  That said, there aren't many surprises here, other than some shuffling in the middle.  The formula believes that Toronto is slightly better than BC (but clearly isn't aware that Ricky Ray is injured), and that Montreal is slightly worse than Hamilton.

1 comment:

Drew Edwards said...

Michael. I'm interested in the advanced statistics work you've done on the CFL. Can you email me at dedwards@thespec.com?

Thanks. Drew