From: dtate+@pitt.edu (David M Tate)
Newsgroups: rec.sport.baseball
Subject: Re: Value of Stats
Date: 28 Jul 92 21:35:25 GMT
Organization: Factors of Ys, Inc.

In article <1992Jul28.202324.12267@ramsey.cs.laurentian.ca> 91287041@ramsey.cs.laurentian.ca (roger maynard) writes:
>In <3845@blue.cis.pitt.edu.UUCP> dtate+@pitt.edu (David M Tate) writes:
>
>>But, and this is the key, the *sum* of those
>>effects can't be any bigger than the variation from what is predicted that we
>>actually observe.  If the model is invariably correct within 5%, then the sum
>>total of all the luck, chemistry, clutchness, etc. is no more than 5% of the
>>process.
>
>I agree with this totally except for the 5% figure.  Are you telling me that
>you can predict the Win/Loss of all teams to within 5%?  Before the case?  Not
>likely.  If you really can I would like to know more about it.

No, I'm saying that if you give me a team's batting stats (AB, hits, doubles,
triples, HR, etc.--how many of each they got, in how many plate appearances)
then I can tell you how many runs they scored, within a few percent.  If you
tell me how many runs they allowed, I can go on to tell you how many games
they won, within a few percent.  This clearly doesn't address such questions
as "Do certain players affect the batting stats of their teammates in positive
or negative ways?", but it *does* say that (for instance) clutch hitting can't
account for more than a tiny portion of team success, since nowhere am I using
the *timing* of the hits in my model.

At the moment I'm not talking about where performance comes from; only about
how individual performances translate into winning.

>>from actual performance.  In other words, there's no place left for those
>>other effects to be hiding, because their variance would show up in the total
>>variation of the process.  

>When you say "quite often" and "essentially all" you are hinting that there
>are inconsistencies in this theory.  Do intangibles have a small impact?

Not "inconsistencies"; just nonzero upper bounds for certain effects.  David
Grabiner has shown, for example, that if clutch hitting does exist then it is
worth no more than three or four extra hits per season for even the most 
"clutch" of hitters.  So, while the effect may exist, it is *essentially*
zero, because three or four key hits, even in high-leverage situations, will
not make as much difference as a significant difference in OPS.  The value of
the clutch hits is smaller than the random noise in the value of ordinary
non-clutch hits.

>How much of an impact do they have? Do winning teams fit the model better 
>or worse than losing teams?

They all fit about equally well.  There are occasional systematic anomalies;
the current Brewers may be one.  This suggests that the current models can
be improved.  

Just as an aside, I'd like to point out again that none of the "stat-heads"
on this net came to baseball with a preconceived idea that it would prove to
be strongly amenable to fairly simple mathematical modelling.  Quite the
contrary; we all came to statistics long after we were baseball fans, with
all the usual baggage about how baseball is supposed to work.  All of us were
eventually converted to the view that most of baseball can be well-understood
in terms of individual performances, without recourse to "intangibles".  It
may well be that, like converts to any belief system, we are somewhat more
vehement in our evangelism than we would be had we grown up with it.  The 
point I want to make is simply that we were all skeptics at one time, and were
convinced by the evidence.

-- 
        David M. Tate        | "And that inverted Bowl we call The Dome
   dtate@unix.cis.pitt.edu   |  Whereunder crawling coop'd we field and bat,
   Edward "Mike" Fitzgerald  |     Lift not your eyes to *it* for help--for it
     from "The Ruthaiyat"    |  Will drop the tow'ring fly upon your hat."
Newsgroups: rec.sport.baseball