Another Look At How Goalies Age: Can we correct for bias?

Graphic Comments
December 10 2012 12:05PM

 Another look at goalie aging

The topic of how goalie age affects on-ice performance came up again last week, first with a post from Steve Burtch over at PPP, followed by a response from Eric T. here at NHLNumbers. Although Steve's post was about the Leafs' quest for an average goalie, he made the observation that "the correlation between goaltender performance and age is nil." Eric's main critique was that the analysis did not take into account "survivorship bias," that is: only the better goalies actually manage to stick around into their late 30s, so this will bias the observed performance of older goalies upward.

In an effort to further the debate, I would like to propose a methodology that controls for "survivorship bias," as well as an alternative way to account for systemic changes in the game that might impact save percentages on the whole.

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Total Player Charts: Conceptualizing Time On-Ice Percentages

Ben Wendorf
December 10 2012 08:48AM

 

 

I've always felt pretty strongly about Tom Awad's now-two-year-old assertion that, absent something better, even-strength ice time is a pretty good proxy for overall player value.

His numbers bore that out. However, I suggested that we could better refine and increase predictability of even-strength ice time by expressing it as a percentage of the team's even-strength time in games the player played (a wordy way of describing 5v5%). Though it will probably be a post in-and-of-itself, 5v4% and 4v5% are both testing to be similarly positive refinements on those TOI metrics.

Rather than handle that today, I wanted to unveil a little idea that had been bouncing around my head for a while. I'll be damned if I can recall the post from Beyond the Box Score, the excellent baseball statistics web site, but they had a season preview a while back where they used radar plots of a number of metrics like OBP, Fangraphs' Baserunner rating, UZR/150 (something to that effect), and for each player on a given team their talent in those metrics filled a certain portion of the radar plot. The more you filled the radar plot, the better you were. Author Note: Having heard back from BtB's Justin Bopp, the creator of the Diamondview Composite Player Evaluation that inspired the Total Player Charts, I can put my agitation and accreditation worries to rest).

There's certainly room for doing this when the statistical hockey gods agree on a metric already (spoiler alert: they never will) - till that time I'm content to build a radar plot of three metrics, 5v5%, 5v4%, and 4v5%. In part, this is to represent player value, as well as where that value gets allocated (just even-strength, or powerplay and penalty kill as well). I'll call them Total Player Charts, or TPCs (which, it turns out, is also an acronym for all sorts of important ish)...you can do a lot of neat stuff with 'em.  

Let's have a look.

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Best of the Nation - 12.9.12

Jonathan Willis
December 09 2012 08:59AM

Lots of interesting stuff across the Nation websites this week, including an exclusive interview with an NHL head coach, 2013 Draft talk, a look at how goalies perform as they age, and obligatory stuff on the NHL lockout. Read more, after the jump!

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ECHL GAME

Wanye
December 08 2012 05:35PM

 

Any league that has the sense not to lock themselves out through Christmas and any team that has the sense to mysteriously drive off Theo Peckham gets our business. Where do you go when there is nothing to do and you are still riding high on having survived a Raiders game?

It's time to go to an ECHL game.

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RAIDERS GAME

Wanye
December 07 2012 05:18PM

With the heart warming news that the Lockout negotiations are extraordinarily poorly, your ol' pal Wanye decided to go to a place where rage and danger are the norm. A place where most people rightfully fear to tread. When there is nothing left to live for you have nothing left to lose. 

Time to take in a home game of the Oakland Raiders.

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