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08-10-2012, 11:56 AM
  #38
Fourier
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Quote:
Originally Posted by mindmasher View Post
Hunh? What is incorrect about his statement? I'm a huge fan of the Oilers and Eberle; I wish him the best, but it's very simple: he performed at a historically unsustainable level and it's very unlikely that he repeats it. Possible, as most things are, but unlikely.

Not even to mention you are trying to someone hold this up as an indicator of advanced statistic misuse - and I see *zero* arguments as to why this is the case. Why is this a ridiculous conclusion? Where are your arguments that his IPP and S% are sustainable and not influenced heavily by a season of good bounces. I would love to see some contrary arguments based on logic, not hand waving.
No one would argue that Eberle is likely to duplicate his shooting precentage. I also do not think it is at all unreasonable to question whether his numbers will drop next year. But so what? The prediction itself is trying to tell us that a player who is almost universally recognized as having elite offensive skills with one of the best shots that I have seen from a player his age in many years is somehow going to regress to the 45-50 point range because his shooting percentage and his IPP is higher than average. This after he put up prorated seasons of 21g and 51pts, and 38g and 81 pts in his first two NHL campaigns. (I use prorated numbers because so far as I know shooting % and IPP are not good predictors of when a player will get injured.) And he did this despite being 5th and 6th respectively amongst forwards in TOI/G, Moreover in his first year he played with a dogs breakfast of line mates and he was 7th on the team amongst forwards in pp TOI/g behind even Linus Omark.

And lets say for a minute that Eberle's S% drops to 12% next year. How many goals will he score? With more ice time does he get more shots. And even if he only scored 22 goals next year, to get into the 45-50 point range his assits total would have to drop by a minimum 14. Why is this so likely. Because of IPP? Is he suddenly going to no longer be a key player in the Oilers offense? Or is it becuase players like Hall and Nuge are going to see big dips in their games as well?

I really wonder if you polled 50 NHL coaches and GM's if you might find one who would actually predict that Eberle would be expected to score in the 45-50 point range next year if he is healthy. If the answer is no, how do you justify such a prediction?

Now you also asked me about why I do not think the use of these stats in the manner we typically ses is appropriate.

At this point we have no idea what Jordan Eberle's mean shooting % will be, but given the nature of his game it is reasonable to believe that it will be comparable with other first line players with very good to excellent shots. But even if we knew what to expect from his S% it is still not possible to predict accurately how many goals he would score. To illustrate this I picked three names of players who I thought might fit this mold at random to look at to see how shooting% might impact their numbers. Here is what there prorated season look like over stretches of their careers (in all cases these three actually played full seasons most years).

Player 1

Code:
G	A	PT	S%
18	36	54	11.8
22	49	71	10.8
36	48	84	15.3
29	45	74	11.7
31	51	82	10.9
Player 2

Code:
G	A	Pts	S%
28	23	51	13.3
31	36	67	11.3
33	43	76	13.5
52	44	96	16.7
38	35	73	11.1
42	33	75	15.5
35	32	67	11.9
46	64	110	14.8
Player 3

Code:
G	A	PTS	S%
18	22	40	12.8
25	29	54	15.2
33	37	70	16.4
38	56	94	17.9
31	30	61	14
43	59	102	15.8
While there is no doubt that S% and goal scoring are correlated, it seems clear that S% alone is actually quite a poor predictor of an individuals actual goal totals.

In player 1 we have two seasons of almost identical S% and yet the goals scored varied by 11 goals. The players linemates were mostly constant over these two seasons at least to the degree that in both years this player played nearly all the time with the same elite playmaker.

Player 2 had far more variance in his linemates and is the type of player that tends to make much of what he gets happen on his own. His numbers are actually closer tied to his S% but the relationship is still far from obvious. For example, we still have two years of 38 and 42 goals respectively despite the fact that the first was his lowest S% of this strecth at 11.1% and thet second was his second highest S% at 15.5%

Player 3 has a lot of similarities in his game to Eberle, but I'd say that it is possible that Eberle's shot is actually better. He has also played a lot with elite plays though these days he plays with someone who is certianly a top end triggerman. Certainly his goal scoring has fluctuated a lot but S%'s of 15.2% vs 15.8% do not explain the difference between a 25 goal season and a 43 goal season.

So I will ask you this. What is are the key characteristics of the statistic S% as a means of predicting goals scored? What does its distribution look like, both for a typical individual and in the cummulative pool? Do we know anything about the variance we might have in using the S% to predict output? What would an 80% confidence interval look like. Is it possible that the top 40 scorers in the league may not follow similar patterns to the masses or is it possible that this analysis is being done using the characteristics of a fair coin when what we have is one that is significantly loaded? .

Without understanding the characteristics of its distribution what predictive value is a statistic really? Without communicating these characteristics why should we put any significant value in any preditions that result from the data if they do not agree with empirical evidence? Can you personally give me any clear mathematical evidence, and by this I mean evidence that a pro might actually accept, that these stats have any real predictive value? I've never seen it.

I should add though that I have no problem with people trying to find gems in the huge piles of data that the NHL generates. There is some interesting stuff. But it has been my experience that too often people read into it more than it is actually there.


Last edited by Fourier: 08-10-2012 at 08:42 PM.
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