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08-21-2011, 06:38 PM
Czech Your Math
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Originally Posted by plusandminus View Post
I've studied correlations between ES icetime and ESGF+ESGA and they don't necessarily correspond very well, perhaps especially regarding forwards. For example, during 2002-03, I guy like Kowalchuk (who had a reputation as an offensive minded player) had about 1.5 times more ESGF+ESGA played than the average player.
So here we thus have our first bias. ESGF=60 and ESGA=50, will give higher "ice time" than ESGF=50 and ESGA=40, even if real ice time is the same. ?
I'm not sure ice time is so important. If a player is on ice for a much higher % of ES GF+GA than his % of his ice time, that's okay. If he's able to perform at or above the GF/GA ratio of the team as a whole, then the more volume the better for the team. If he's at a worse GF/GA level, then the high volume will negatively effect the player portion of the metric even more.

Originally Posted by plusandminus View Post
I'm a bit against dividing ESGF by ESGA. As i wrote in another reply some day ago, I think there are better ways to do it. To use the above example, I would say that 60-50 and 50-40 is equally good, despite the latter one getting a slightly higher ratio (if I understand you right).
I don't know why you are so against calculating GF/GA ratios. They shouldn't be used randomly, but in this case they are the primary basis of the pythagorean win% calculation, so of great importance.

Whether 60/50 or 50/40 is better may depend most on context (all other things being equal). On a bad team, the extra 10/10 might be helpful, while on a good team, it may be hurtful.

Originally Posted by plusandminus View Post
I googled, and according to wikipedia I got the impression that rather 1.8 was the "right exponent", at least in baseball?

Wouldn't shootout goals be excluded from the stats?
I saw more than one study for hockey. If 1.8 or whatever number is deemed a solid number, I have not attachment to 2.0 as exponent. It does vary by sport though, I think mainly due to differing scoring levels.

Originally Posted by plusandminus View Post
That's 94-38 = +56 with Forsberg. And 84-87 = -3 without.
Not only did he have the league's by far best ES+/-, and scored the highest amount of ESpts, on a team that without him (and the guys who were on the ice with him) had negative +/-.

Adding ESGF+ESGA, we get 94+38=132 for him. 178+125=303 for the team.
That's an "ice time" of 43.56 % according to ESGF+ESGA.

I got 43.56 %, so at least one of us (perhaps I) may be wrong.

In reality, the correct answer seems to be 28.84 %. (if my data is correct)
So, the estimated percentage is about 1.5 times higher.
You are correct. I have realized yet another error in this hastily put together study. I had calculated player's % of team's GF and GA separately and then summed them, instead of summing them before calculating the player's % of team. I came up with this idea a couple days ago and used some existing player data for the basis of most of the calculations, but that doesn't excuse my sloppiness.

Nice job of checking my math!

Originally Posted by plusandminus View Post
And I think three players with identical EStime, having ESGF-ESGA of 40-40 and 30-30 and 20-20 contributes equally much.

Originally Posted by plusandminus View Post
It would be interesting to this stat listed for all the players on a team.
(I can do it myself, but not right now.)
With the risk of being called an idiot, does the sum of all players equal 100??
I don't have calculations for an entire team. I think the totals would not exactly balance, but should not be way off either.

The total for all players on the team should be somewhere around:

5 * 82 * (team's ES pythagorean win%)

note: 5 is number of skaters per goal

For a team with equal ES GF and GA, should be ~205 "ES wins"

Originally Posted by plusandminus View Post
Pittsburgh were a bit special that year, starting the season with some very good players, just to see them drop off one by one. So Mario's stats sank deeper and deeper during the season. (If I remember right.)
Yeah, Pittsburgh was real "special" for a few years there post-Jagr.

In '94 and '96, Lemieux's R-On was slightly less than R-Off, although a big reason for that is Jagr being such a large part of the R-Off. His R-On/R-Off is great in '97 (1.97) and very good in 2001 (1.39), but a lot of that was due to those being the 1.5 seasons he played with Jagr at even strength. After that, he was mostly weak.

Originally Posted by plusandminus View Post
A thought I have, is that one might want to seperate forwards and defencemen, since they may not be easily comparable.

An additional way of improving (or not) the method, could be to include ESpts in the calculations, to estimate how much different players contributed to their ESGF. Now I'm mainly thinking of doing it for forwards, to help seperate the offensive contributions of linemates, although it might be useful to apply (perhaps in a differnt form) to defencemen as well. To do something similar for ESGA would of course be basically impossible (unless one apply an assumption like "defencemen being more responsible for ESGA, while forwards being more responsible for ESGF").
Yes, separating forwards and defensemen is one possibilty. Would rather not do that... and what about players like Coffey that could almost be classified as either? I like using a player's ES points as a % of ESGF, but this requires even more data and doesn't address ESGA. I think the latter is probably the better way to go, or it may be better to just live with a "pure" but flawed metric.

Originally Posted by plusandminus View Post
Finally, which you likely are aware of, this stat only tells us about players' contributions during ES. So the "rankings" here are ES only.
Creating similar stats for PP and SH would rank players differently.
For example. While Forsberg had "much better" ES stats than Naslund in 2002-03, Naslund had better PP stats.
Of course this, like adjusted plus-minus, isn't an all-encompassing metric. It's meant to shed light on even strength value. Still, about ~75% of goals occur at even strength and it's even strength play that leads to penalties, so ES play is crucial to overall value.

It's not meant to measure all aspects of the game.

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