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04-29-2012, 01:47 PM
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Originally Posted by plusandminus View Post
Just to make sure, what formula and project do you refer to?
You mention 1st lines, but is that really so "black and white"? It seems that many players move around a lot between different lines?

When I wrote here yesterday, it was about the simple kind of situational estimations that focused only on situational GF+GA.
Estimated ES icetime = ESGF+ESGA / teamESGF+teamESGA.
Estimated PP icetime = PPGF+PPGA / teamPPGF+teamPPGA.
Estimated SH icetime = SHGF+SHGA / teamSHGF+teamSHGA.
The above results in percentages. So as in the Stevens/Niedermayer case, I focused only on SHGF+SHGA.
my mistake, you made it sound like you had done work using the actual TOI file that we've been referring to. It sounds like you're referring more to overpass' method of estimating PP/PK usage.

What I was saying is, in the TOI file where GF/GA in PP and PK situations are used to determine TOI, there is probably an adjustment for top unit players that accounts for the fact that they score and get scored on more often. This would "smooth out" the effect you're seeing in the extreme Niedermayer/Stevens example.

Let's take a made up example:
Two of the defencemen got correct rankings, while two didn't. 50 % correct. Sometimes the ranking was correct, sometimes off by 1 placement, sometimes by more.
I wouldn't necessarily call that an error. It does, however, underscore the importance of looking at the actual numbers and not getting caught up in rankings. You're right that there can easily be differences from actual to estimated results; I think that this would only happen in cases where they were very close to begin with. And I don't think it would be very often that estimates would change this. i.e. if you're close in actual numbers you'll be close in estimated numbers, and I don't think it should really concern anyone if one player is 30 seconds ahead in actual numbers and 30 seconds behind when estimated; this is not a huge deal. People should be getting away from the whole "see, he was the #2 defensemen because he played 30 seconds more than the #3 guy" mindset and more towards the "these two guys played about the same minutes, you could say they were the co #2/3" mindset.

When I asked about errors I wanted to know about differences in the calculated times. When you say that it might swap who the #2 and #3 defensemen are, it might only take a 10 second swing to make that swap, or it might take a 3 minute swing, so it really says nothing about the quantity of the error.

So let me rephrase the question - how often are the estimated results more than 10% away from the actual results?

I too think that they basically pass the "eye-test" in the way you describe here. But I still think they may be up to 1-4 minutes wrong for the top players. If one player ends up with 28:22 per game, and another 29:20, I think we cannot be sure at all which one of them that actually had more factual icetime.
To keep to the original topic of this thread, that really shouldn't matter much anyway.
I agree that this really shouldn't matter either, as per the above.

My main concern might be to be careful to distinguish between what we do know and what we don't know.
For stats from say 1970-71, we just hame GF, GA, PPGF, PPGA. An estimation is being made to calculate ESGF, ESGA, SHGF and SHGA. After that, those numbers are being used to estimate situational icetime shares within teams. After that, we estimate how much situational icetime each team as a whole might have had during the specific season. Then we combine the first estimation(s) with the last, to get our final result.
True. Keep in mind that the estimate of how much situational icetime a team had in a season is a very easy thing to estimate. You know how many PPs they had for and against, and we know the average length of a PP over time. As long as a team didn't have a massively dispropotionate propensity to score PP goals very early in the PP, or allow then really late, then those numbers are pretty solid indeed.

Maybe icetime in itself shouldn't be the ideal criteria anyway? Maybe "a minute is a minute" isn't the best way to approach this, as it is so often pointed out that there could be a significant difference between a "hard" minute and an "easy" one?
Yes and no. Typically more minutes = tough minutes because the more minutes one plays, the less likely it becomes that they are being "sheltered" from the other team's best players and crucial situations.

In more "hockey" terms, it's really unlikely that a coach says "I like this player so much that I'll give him all kinds of minutes, but he scares me so much that I'll never use him in important situations."

Well, basically it does. There surely is a strong correlation between minutes played and goals on ice for. The more one plays, the more goals one will be on ice for, even though the pace may be different for different players. I do think it passes the smell test overall, but in cases of a less than 2-3 minutes difference I think one should keep an open mind to that we don't know for sure which player actually played the more minutes. And we certainly don't know everything about the quality of the minutes.
I agree, and as I said, I don't think we should care too much.

By the way, here is a curiosity that I've been thinking about. Lidstrom has several times led the best team in the league in icetime. Sometimes he has even has had the most ES and PP and SH minutes on the team, despite playing on such a great team. How come? Is it because he has greater endurance(?) than other players in the league? Wouldn't one expect every team to have their 1st defenceman logging huge minutes? An average defenceman playing on a team with poor defencemen should be able to have the same role as Lidstrom has in Detroit and log similar numbers. Yet it's often the best defencemen of the league that ends up with the most minutes. (I haven't studied this yet, it's just a more or less spontanous thought.)
I have my own thoughts on this, but not sure this is the time and place.

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