From: kbos@carina.unm.edu (K. Mitchell Bose)
Subject: Re: defensive measures of performance (was -- Re: Lists: The Best Players In Baseeball)
Date: Sat, 09 Jan 93 12:00:56 GMT
Organization: University of New Mexico, Albuquerque
Distribution: na
Keywords: RF, DA, ???

In article <1993Jan8.205929.9120@athena.mit.edu> cmk@athena.mit.edu (Charles M Kozierok) writes:
>In article <steph.726521280@pegasus.cs.uiuc.edu> steph@pegasus.cs.uiuc.edu (Dale Stephenson) writes:
>>In <1993Jan8.032738.23621@athena.mit.edu> cmk@athena.mit.edu (Charles M Kozierok) writes:
>>>based on your comments, and the post by Clay where he explains
>>>what the DA and RF are (thanks, btw), i would have to conclude that
>>>these statistics definitely are bogus. i don't know why anyone would
>>>use them to judge much of anything. i know i wouldn't.
>>
>>Why use it?  Because, (lousy as it is) it's the best I have available to me.
>
>all i will say is that a lousy statistic is *worse* than no statistic at all.
>i believe that should be self-evident.

Range Factor was a ten or fifteen year old first attempt to create an index 
that provided a better look at defensive prowess than fielding percentage.  It's
been attacked for not being anything more than what it is, from people who 
want it to be more.  There are some very valid criticisms, but by and large,
it's misused.  Year-to-year correlation, for example, is more useful for RF
than one-year ratings.  (As an aside, another bias that works against Alomar is
that (at least through 1991) he hasn't mastered the double play, and the assist
part of RF works against that.)

>i understand your predicament, but i personally would rather have no answer
>than the wrong one. and we have already seen at least one example where
>a player has been misjudged due to this stupidistic (tm).

Ah, and one error, of course, invalidates the entire process.  We all know that
because Cal Ripken, who _always_ gets 20 homers in a season, hit only 14 this
season, we can toss out home runs as a measure of power.  :)  (Kidding...)

All range factor ever meant for Bill James was an improvement over fielding
percentage.  

For instance, RF is either plays made or plays involved in per nine innings, 
depending upon whether or not one adds errors to the numbers.  As was posted
earlier, the offensive analogy was hits per game.  Not very good, right?  Right.
However, up to that point, the only other thing on the market was FPct., for
which the best offensive analogy I could come up with is hits divided by the
number of hits some guy in the press box thought the batter should have had.
The offensive analogy for the way writers hand out the Gold Gloves?  Hmmm.  I
guess Gold Gloves are the best analogy, come to think of it.  :)  Actually, it's
the highlight film, which is why Carney Lansford got so much praise for his
spectacular diving plays when it was IOTTMCO that the man had zero lateral
movement.

Anyway, zone ratings and defensive average both measure plays made, but the
divisor in this case is not games or innings, but opportunities.  Basically,
the idea is that if a ball is hit near you, you should catch it.  Simple, no?
It's like using batting average to rate players rather than raw hits.  If a
player doesn't get many opportunities, due to flyball pitching or the like,
then he'll be judged on the basis of only those opportunities he did have.
The difference between the two is, as far as I know, zone ratings require the
fielder to be responsible for a smaller area than defensive average.  Thus,
zone ratings are beneficial to the fielder with surer hands, while defensive
average helps fielders with wider range.  In much the same way, batting 
average helps the player that makes contact with the ball and hits it into the
gaps, while on base percentage helps players with better plate discipline.

What needs to be done to improve both DA and ZR is to chart where ground balls
are hit (or fly balls, whatever), and use individualized hit ball charts for
each hitter and pitcher to modify the zones for which each fielder is
responsible.  With the backing of STATS and Project Scoresheet data to get those
modified charts, a refining of DA and ZR will surely come, adjusted better.
Still, play-by-play data and fielding charts haven't been widely available for
long, and both DA and ZR are but five or so years old.  Even now, the wizards
at Stathead U. are working to solve the remaining problems, or at the very
least, compensate for them.  :)

>>It's really kind of frustrating, because it less useful than having batting
>>average without OBA or SLG.

As above, range factor isn't like BA; it's like hits/9 innings.  Yecch.

>>So why use it all?  My alternatives would be 1) Error Totals, which is worse
>>than range, and 2) Gold glove voting. Given who does the voting, I find it
>>hard to believe that it correlates better with reality than range factors.
>>In individual cases (Alomar?) it might, but as a general rule?
>
>you sound like a smart guy. invent something better! start with one
>of the stupidistics and make the necessary adjustments. or start with
>a clean slate.

What do you think has been going on?  The next generation is DA and ZR.  Next,
working out the necessary adjustments is going on, I'm sure.  And if a clean
slate is required, as it was when going from RF to DA, it will be done.  The
1992 Blue Jays weren't built in a day, Chas.  :)

>>And defense *is* important, and should be talked about.  So I can't leave it
>>alone.
>
>then i think we should at least attach a good-sized list of caveats to
>any evaluation that uses those stats.

Isn't that what we've been doing with RF by admitting its faults?  I'd admit to
the faults of DA, but I figure Sherri Nichols oughta do it first.  Besides, I'm
busy, and converting you to the Order of the Slide-Knuckle-Change Rule isn't
that high on my list. :)

>>Shouldn't they try to put him {Alomar} in
>>a package for Frank Thomas and sign Jeff Treadway to play second? Now, these
>>doesn't help a great deal when comparing players.  But both Sandberg and
>>Alomar are considered fine defensive second baseman.  But Sandberg helped his
>>team more defensively, as far as I can tell.
>
>depends on the purpose of the comparison. some people misinterpret what the
>statistic means, and don't realize that Alomar would help his team a lot
>more than Sandberg does if Alomar was a Cub (shudder...)

Defensively?  He's still not that great as a pivot man on the DP, Ryno's hands
are about as good, and Ryno still has great lateral movement and an accurate 
arm.  I'm thinking that you're including offensive performance in that last
statement, and I agree wholeheartedly with it if so.

>
>saying Alomar is less valuable to his team is fine, as long as that
>isn't projected onto Alomar himself. which has been done. that is my
>objection.

I think, FWIW, that Ryno is as valuable to the Cubs, or more, than Robbie is to
Toronto.  However, Alomar would be a hell of a lot more valuable to the Cubs
than Ryno would be to the Jays.

>>Defensive Average makes sense to me.  It's going in the next revision of my
>>baseball game.
>
>what about park effects? how can it be of any value without park effects?

The same way batting average can be of "any value" without park effects.  The
same way ERA is of "any value" without park effects.  Gross differences in 
performance are still conclusive; adding park effects just increases the
precision of the measurement.

>surely you could do better than the current definition.

And we will.  But the current definition is better than the whim of a scorer,
or the effect of ballet moves on a reporter's opinion.  Kinda like when Kelly
Gruber would get brownie points from the media for sliding into first when it
was clear from timing him that sliding got him into the bag first slower than
when he ran through the bag.  One of the heartbreaks of numbers is that they
keep the style and color out of the judgement.  It's also one of their 
strengths, when the aim is not appreciation, but analysis.

>>But I believe that *if we had no better statistic available* RBI totals *would*
>>be more accurate than a random distribution in assessing worth, and most
>>likely would be more valuable than the Mediots assessment.  IMHO, of course.
>
>but that is why we use more intelligent stats like SLG.

Maybe you're not reading correctly.  "IF WE HAD NO BETTER STATISTIC AVAILABLE".
In the case of RF (or, now, DA), we didn't/don't.  The search goes on, the
models are revised, and better alternatives are found.  But remember:  
offensively, we've had 100 years to develop alternatives.  We only started 
paying as much attention to the defensive side a few years ago.  DA isn't an
end; it's a step.  That's all it claims to be.  Do I trust it more than my own
eyes?  Not when I can see the same player for 80-100 games.  But when I only
get twele or thirteen games a year to see another team, and maybe ten or eleven 
to see another player, and another fifteen to twenty times I can see a player
on TV, and I only see that player for five seconds or so each play, and the
other 100-120 games all I see are maybe a total of fifty of his "spectacular"
plays, hell, yes, I trust that more than my own eyes, because I only get a
handful of chances to actually _see_ the guy set up for a play, or land after
turning two, or getting a jump on the ball each year.  If a player isn't on
a team I see three or four times a week, I can't form a reliable opinion on
him.  And I'm a former shortstop.

>>Note that Defensive Average does not suffer from the distribution problem,
>>and therefore is much more reliable than range factor.  It still may suffer
>>from park effects, and of course distribution of "hard" chances, but I'm
>>inclined to believe those effects would be minor.
>
>really? how can playing on turf versus playing in the "heavy rough" in Detroit
>not have a significant effect on ground balls? i find that *very* hard to
>believe.

How much is "significant"?  How much does the ball slow down, and how much
more movement does that let the fielder cover?  If it adds, say, one step in 
either direction, or perhaps, to keep it in perspective of distance, a two
degree arc covered by a fielder on grass and not on turf, that'll increase the
number of plays made by about 10% on grass, in an on-the-cuff calculation.
Maybe.  Play-by-play data would help.  Alomar plays 99 games on turf, and 63
on grass.  In Tiger Stadium, he would play 24 games on turf and 138 on grass.
With a 1992 RF of 4.68 in SkyDome, a little algebra works out to a comparable
4.89 RF in Tiger Stadium, again using my rough back-of-the-envelope 
calculations, for a 5% rough increase.  Add that to the other errors people 
have mentioned, and you bring him up to a little above average.  That's about
where ZR puts him, and DA rate him higher.  None call him the best.  But think
about it: he's not particularly good on the double play, and at least one 
other poster called him "inconsistent", a charge I won't support or refute.
I'll simply say that I agree that Alomar is a good, not dominant, fielder who
has lots of the problems with range factor work against him.

>>I definitely have more faith in it than in subjective judgement.
>
>well i understand not wanting to use a subjective judgment. but DA sounds
>pretty bad, even if better than RF. your decision to use DA instead of
>subjective judgment sounds primarily like a... well... subjective judgment.

Well, for someone who, if I remember the thread correctly, had a cursory 
explanation of DA given a day ago and is already pronouncing it DOA, your
casual dismissal of the index sounds like a subjective judgement, made on even
less of a sample size than subjective, in-person fielding judgements.  :)


-- 
Kurt Bose (as in Daisy, not Rose) * kbos@carina.unm.edu * Walks: not that sexy.
"Halt!  Based on conclusive dental evidence that truly bites, I arrest you 
 hereby for the murdering of the dead Belzic Tascar.  I am obliged to warn you 
 that my weapons are registered as offensive fronds!!"- R.M.Allen, "Monkey See"