Wednesday, May 28, 2014

Corsi and Fenwick suck, or why we should be trying to do better

I think Corsi sucks.

I think Fenwick sucks.

I think they suck, not because I'm an old-school, Brian Burke-ian stats hater. I think they suck because when it comes to "advanced" hockey stats, the formula shots +  blocks + misses = corsi is lazy and oversimplistic. I think they suck because (at best) they're weak proxies for what we believe is important in a hockey game (puck possession). I think they suck because I know we can do better.

Mostly, I think they suck because they're a constant reminder of the fact that there's so little investment in hockey analytics by teams and by the media. Don't get me wrong, there's fantastic work being done by lots of people on the blogosphere, but until NHL invests in player tracking technology (and hopefully makes it publicly available) we're going to be stuck using weak proxies like Fenwick and Corsi to measure possession.

In this post I don't intend to bring you to my side. You probably clicked on this post precisely because you know what Fenwick and Corsi are and find them valuable. I agree with you on that. They're infinitely better than plus/minus and other run-of-the-mill stats. But until we get player-tracking data and other more sophisticated stats, I think it's important that we understand how to properly use Corsi and Fenwick.

The point of this post is to convince you that Corsi and Fenwick don't do a particularly good job of predicting who will win hockey games, and they aren't any better at this task than the traditional shots-on-goal statistic. I also hope to build our understanding of the types of questions that Corsi and Fenwick can answer and when it's appropriate to use them to build narratives about games. Right now I'm mostly concerned with team-Corsi and team-Fenwick, not individual player Corsi/Fenwick, but in the future I'll hopefully dive into the value of C/F on assessing player performance.

Monday, April 14, 2014

2013/2014 win probabilities - Central Division

Below are the videos which show the win probability graphs for all 2013/2014 games for the teams in the Central Division. To learn more about the win probability metric, check out my post here. The folder with the individual game graphs for every team is available here.

2013/2014 win probabilities - Pacific Division

Below are the videos which show the win probability graphs for all 2013/2014 games for the teams in the Pacific Division. To learn more about the win probability metric, check out my post here. The folder with the individual game graphs for every team is available here.

2013/2014 win probabilities - Metropolitan Division

Below are the videos which show the win probability graphs for all 2013/2014 games for the teams in the Metropolitan Division. To learn more about the win probability metric, check out my post here. The folder with the individual game graphs for every team is available here.

Sunday, April 13, 2014

2013/2014 win probabilities - Atlantic Division

Below are the videos which show the win probability graphs for all 2013/2014 games for the teams in the Atlantic Division. To learn more about the win probability metric, check out my post here. The folder with the individual game graphs for every team is available here.

How much smarter are college basketball experts than the rest of us?

I wrote an article this week for Deadspin looking at how much better college basketball "experts" did at predicting the NCAA tournament this year than non-experts. I used the same 11 million brackets from ESPN.com's Tournament Challenge as I used for the earlier article in the Wall Street Journal. Perhaps unsurprisingly, the experts didn't do all that much better than the non-experts.

"Generally the experts' brackets were slightly better than the non-expert ones, although the evidence isn't especially overwhelming. The analysis suggests that next year you'll have just as good a chance of winning your office pool if you make your own picks as if you follow the experts."

I've also made the data available here.


Tuesday, April 8, 2014

Odds of a perfect NCAA bracket this year

Check out my new, non-hockey, article in Monday's Wall Street Journal. I find that, this year, there was a 1 in 1.47 quadrillion chance of picking a perfect NCAA March Madness bracket.