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08-17-2012, 03:31 PM
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Originally Posted by barneyg View Post
Nice work btw. I just want to make two comments that I hope will be constructive.

I have read the article and I believe it is ill-suited for your purpose here (which is about ranking the league's best d-men among themselves). That article's conclusion is based on eyeballing a histogram for 3 Flyers players and showing that Nodl's expected Corsi (49.5%) is "only" 1.1% lower than Betts' (50.6%). Well guess what, the range in Corsi between the league's best and worst players is only ~12% (44-56) according to the article, so a 1% difference is significant! If d-men are uniformly distributed on Corsi and if there are 200 d-men in the league (6-7 regulars per team), that means the d-man who'd be 16th against good opposition could be 1st against mediocre opposition! If the uniformity assumption is wrong, he could leapfrog even more people.

Long story short: If you looked at the whole universe of d-men, then it may be true that QOC wouldn't really matter -- a guy ranked #50 out of 200 could really be 40-60 and it wouldn't matter. But if you're going to rank the league's top 10 d-men, QOC could make you conclude that a guy is ranked #2-3 when he should really be #10.

(I don't know how you can arbitrarily exclude Yandle on QOC and then make the claim that QOC is insignificant. I understand why you do it but to me it's just further evidence that QOC makes a difference, we're just not sure how to account for it.)

"+/- relative to team" wouldn't pick up that effect as Behindthenet's "+/-OFF" only includes games for which the player actually played, i.e. if the Pens sucked while Letang was injured, it didn't affect his +/- relative to team because those games aren't considered. You can easily convince yourself of this by looking at d-men who have played very few games, their +/-OFF is all over the place. (ex: Sneep, Bortuzzo and Strait on the Pens)
Not sure I entirely understand the first part of your post (sorry it's been a long week ) but thanks for sharing about the +/- relative to team, didn't know it was already adjusted to only include games you played in...makes the Letang results very interesting (though as you said, QoC is something to consider).

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