Thursday, December 12, 2013

Why popular advanced stats are bad at predicting who wins hockey games

Check out this post on the new version of Rink Stats.
A few days ago, Jonathan Willis at Bleacher Report had a great article introducing his readers to a few of the most common NHL advanced statistics. He breaks the stats up into team statistics and player statistics. For team stats he mostly focuses on Fenwick and Corsi, which are the two most popular way that hockey analysts like to measure shot attempts.

Fenwick and Corsi are commonly thought of as a good way to capture how much a team is dominating offensively, since teams only attempt a shot when they're in their offensive zone. In other words, Fenwick and Corsi are thought of as proxies for how much time a team spends in their offensive zone. A natural conclusion to draw from this is that if your team dominates your opponent in the Fenwick and Corsi stats, then most of the game was likely spent in your offensive zone and your team probably won the game.

In this post I'm going to dig into Fenwick and Corsi and show that neither stat is very good at predicting who wins hockey games in the NHL. In fact, I'll show that the simple shots-on-goal stat does a better job at predicting who will win a game than Fenwick and Corsi.