From: grabiner@math.harvard.edu (David Grabiner)
Newsgroups: rec.sport.baseball
Subject: Re: RC/MLV Study
Date: 4 Oct 92 17:48:13 GMT
Distribution: na
Organization: /etc/organization
In-reply-to: josh@cbnewsh.cb.att.com's message of 4 Oct 92 13:53:08 GMT

In article <1992Oct4.135308.26176@cbnewsh.cb.att.com>, joshua.h.rosenbluth writes:

> Here are some notes on a study in progress comparing Marginal Lineup Value (MLV)
> to Runs Created per Out (RC/Out) for evaluating offensive individual
> contribution:

>    *  I took each of the 92 AL players with at least 400 ABs from
>       1991.

> The results to date are:

>    *  RC/Out overestimates value.  A good first-order approximation
>       is take .79*RC Value to get MLV.

>    *  RC/Out's overestimation decreases as a player's SLG-to-OBP ratio
>       increases.  That is, if you have two guys with the same RC/Out,
>       one of which is a slugger and the other is an on-base guy, the RC
>       prediction, based on surrounding a player with 8 clones, does a better
>       job for the slugger (Why?  What does this mean?).

The reason for this is the error that RC makes when it multiplies a
player's SLG by his own OBP.  The value of a homer does not depend much
on the player's other stats, but with RC, the players who have the
highest OBP get the most RC for their power, and those with the highest
SLG get the most RC for getting on base.  Since players with a high MLV
usually have both high OBP and high SLG, their RC will be higher than
their MLV.

An average player, with .320 OBP and .400 SLG, gets .96 added to his RC
for the three extra bases when he hits a homer, in addition to the value
of a single.  Cecil Fielder, with .320 OBP and .500 SLG, also gets .96
added to his RC for the extra bases on the homer.  Robin Ventura, with
.380 OBP and .420 SLG, has about the same MLV as Fielder, but gets
1.14 added to his RC for the extra bases on his homer.

Thus Fielder's MLV and RC value will be about equal.  He gets the correct
value for his power.  While RC overvalues his getting on base, he is
average at it, so the excessive value gets multiplied by 0 in computing
his net value.

Ventura's MLV will be lower than his RC.  RC overvalues his power, which
is slightly above average, and also overvalues his getting on base,
which is well above average.

>    * Finally, doesn't this all mean that the top pitchers are worth
> more compared to the top hitters than we previously thought.  RC/Out
> has its largest errors for the greatest hitters.  Take a look back at
> the 1987 Bill James Abstract and read his evaluation of the 1986
> Mattingly/Clemens and 1978 Rice/Guidry MVP debates.  Is James aware of
> his mistake?

I'm not sure.  There are at least two places in the Abstracts in which
James mentioned this flaw.

1988, in "Rain Delay" [quote is approximate]: Boggs was 82 runs better
than an average 3B last year... but the runs created formula may
overvalue a player who has both a high on-base average and a high
slugging average.  [Boggs hit 24 homers that year.] Even if we drop
Boggs ten runs because of Fenway and another ten because the runs
created formulas aren't perfect, that still leaves him with +62.

1985, Jim Rice comment: James points out that Rice had a terrible OBP in
the RC formula, because he was penalized for taking 35 other runners off
base with his double plays.  He therefore argued that Rice may have
actually created more than the 88 runs that the formula said.  After
adjusting for the fact that Rice's 1984 season was also not a typical
season, he moved Rice up from ninth to third among AL left fielders

--
David Grabiner, grabiner@zariski.harvard.edu
"We are sorry, but the number you have dialed is imaginary."
"Please rotate your phone 90 degrees and try again."
Disclaimer: I speak for no one and no one speaks for me.