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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The Players And Owners Might Get Back To Work, But What's The Fan's Way Back?

Brent Morris
December 06 2012 10:41AM

 

 

Writing about CBA negotiations is tricky - by the time your article appears, the winds may have totally shifted. This article may indeed look ridiculous tomorrow.  

However, we stand today on Thursday, December 6 with the owners and players in talks for the third straight day, and while conflicting reports come out about the state of each side, it's been made clear that both groups are incredibly close on most issues.  

It feels like the home stretch.  

Fans on Twitter are getting a little excited. Of course, fans on Twitter don't make up the bulk of the NHL-going public - those who tweet about hockey are the die-hards. The league could lock out for 3 years and we'd follow all the court machinactions with the same passion we watch the games. What's going to get your Gordie Schmo and Wendel Six-Pack back in front of the TV watching Hockey Night in Canada? 

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It’s nice to be wrong

Jonathan Willis
December 04 2012 10:59PM

An NHL lockout is a cynical business, with two extremely rich parties fighting for a wicked pile of cash. The most recent edition has been particularly galling, with two sides seemingly able to agree on a myriad of issues but unwilling to bridge the small gap between them.

Given that, naturally I was cynical about the December 4 meeting between players and owners – without the presence of league commissioner Gary Bettman or NHLPA executive director Donald Fehr. I thought it likely to be an empty ploy without hope of succeeding. And to be clear: it hasn’t succeeded yet. But for the first time in quite a while, things are looking up.

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NHL OWNERS AND PLAYERS FACE-TO-FACE

Jason Gregor
December 04 2012 08:21AM

Donald Fehr and Gary Bettman will not be directly involved in today's meeting between six NHL owners and a select group of NHL players, but don't jump to a conclusion assuming that both sides will suddenly find some common ground with their leaders out of the room.

Bettman has long been the player's whipping boy. They actually believe that he wants to ruin the game and that he's the ultimate puppet master pulling the owner's strings. Meanwhile the NHL is certain that Fehr is not telling the players the truth, even though many of them have been present during most of the negotiations.

The lockout was asinine to begin with, but it's becoming more laughable by the day. It would be great if today's meeting will start an avalanche of positive negotiations, or as Steve Burton reported continue on the "significant progress" they allegedly made yesterday.

We'll see.

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Adjusting Time On-Ice: Can 5v5% Tell Us More About TOI?

Ben Wendorf
December 03 2012 12:57PM

 

 

Dealing with sum data should inevitably make a fancy stats person a bit uneasy; sums perpetually have a wealth of additional factors a person needs to know before they try to conclude anything. For instance, let's say your team's prospect is Lukas Sutter, and you want to know what the hell is going on with his point totals (aka, sum data). Well, Sutter's ice time is suffering right now, and the penalties he's taking aren't helping him get out of the doghouse. Hence, low points. Let's also say I'm predicting that, had the season happened, Evander Kane was going to score 50 goals...would he be taking enough shots? Will he play enough games? Will he receive enough ice time? Et cetera, et cetera...

Well, one of my previous posts pointed out two things we know about team 5v5 time on-ice: a) it can be volatile and independent of team talent, and b) it has gradually increased over the years. This throws a little bit of a wrench into using raw 5v5 TOI/60 to look at player quality, although that wrench can pretty easily removed.

First steps

My thinking is that you could control for those two elements of volatility by taking a player's 5v5 TOI and divide it by the team total 5v5 TOI in the games the player played. Whenever you do something like that, you want to make sure that you're actually improving predictability and either easing access to or learning new information, otherwise there's no point in creating the new metric. So, how did creating 5v5% work for me?

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