Steering advanced regression tools towards modern hockey thought

Eric T.
June 12 2013 12:20PM

Tyler Dellow recently observed that hockey analysis is encountering a problem that has been a significant issue for analysts in other sports.

In short, the community does not get as much out of people with expert technical knowledge about statistical analysis as it could because those people are often unaware of much excellent work that has been published on blogs and therefore direct their high-powered tools towards outdated problems.

Yesterday on Twitter, an academic paper ("Estimating player contribution in hockey with regularized logistic regression") made the rounds and received some criticism. I have emailed the authors to make suggestions in the hopes of helping get them up to speed on what is already known so that their future analyses can do more to advance the community.

The text of that email is below.

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Zone entries and the Sloan Sports Analytics Conference

Eric T.
February 20 2013 11:18AM

Dump and carry-ins
Image courtesy Shaun Kreider, Kreider Designs

NHL Numbers previously published a couple of articles on zone entry tracking. We first looked at the results in Flyers games from 2011-12, observing that shot differential at 5-on-5 appears to be largely determined by neutral zone play, and that retaining possession as a team enters the offensive zone is particularly important, generating more than twice as much offense as a dump-and-chase play.

We then called for volunteers to join the project and have had a number of people contribute. We have expanded our database to include a full season of data from the Wild, a half-season of data from the Sabres, a half-season of data from the Capitals, and over 100 assorted games from other teams in 2011-12. This has allowed us to further generalize and strengthen our conclusions for a paper that will be presented at the MIT Sloan Sports Analytics Conference.

You can read that paper here.

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How goalies age, and the survivorship bias problem

Eric T.
December 06 2012 02:10PM

Brodeur
Older goalies can still get the job done, but sometimes they need to sit down and rest for a bit.
Photo by rubyswoon via Flickr

This morning, Steve Burtch published a study arguing that goalies do not show any appreciable decline with age. The key plot was this one, in which the x-axis is the goalie's age and the y-axis is how many standard deviations above or below league average he was (for goalies with at least 30 games played):

Goalie vs age

It's clearly true that the observed performance of old goalies isn't appreciably worse than the observed performance of young goalies. The problem is that word "observed" -- we don't get to observe the performance of all goalies at all ages. JaredL previously looked at this issue and showed how few goalies continue to play heavy minutes into their late 30's. This creates what is called a survivorship bias.

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Reference library: Variance and regression

Eric T.
November 14 2012 04:50PM

This article is part of the NHL Numbers reference library, which seeks to collect articles from around the web that have contributed to our understanding of the game.

This page is devoted to articles that look at the role of variance and regression in hockey. This will include looking at how much variance a given statistic has and whether it reflects a true talent, how actual performances compare to random chance models, etc.

We need your help to keep the library complete and up to date -- contact me on Twitter (@BSH_EricT) or via email (bsh.erict -at- gmail) with suggestions of articles you think we should consider adding.

Return to the library main index.

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Older players and the grind of a long season

Eric T.
November 13 2012 02:31PM


I've often heard it suggested that players wear down over the course of a season.

When I wrote about whether players elevate their game in the playoffs, multiple people in the comments argued that players can and should conserve energy during the regular season. It's a particularly common suggestion for older players, who are presumed to be more prone to fatigue. Guys like Jaromir Jagr and Teemu Selanne hate taking days off, but players and coaches are so convinced that they will wear out that they insist on it.

I'm not a physiology expert by any means, so I'm not qualified to make direct assessments of whether older players will suffer more cumulative fatigue than younger players would. However, I am capable of looking at whether such fatigue is born out in the stats.

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