From: genetic+@pitt.edu (Dr. Dave)
Newsgroups: rec.sport.baseball
Subject: Re: NL ROY: More Fuel for Debate
Date: 30 Sep 92 17:33:14 GMT
Organization: Department of Industrial Engineering

Thus spake claudius@leland.Stanford.EDU (Nelson Lu):
>In article <6479@blue.cis.pitt.edu.UUCP> genetic+@pitt.edu (Dr. Dave) writes:
>>
>>Lineups, yes.  People, no.  If 9 Barry Bondses would score 12 runs per game,
>>and 9 Terry Pendletons would score 7 runs per game, is Barry Bonds worth 5
>>extra runs per game over Pendleton?  Of course not; 

>But where do I claim that Bonds is worth 5 runs a game over Pendleton?
>Nowhere.  I claim that Bonds is worth 5 runs more to his team if both he
>and Pendleton make 27 outs.

But that's not true, either.  You're saying that one Barry Bonds would
contribute just as many runs per out in an average lineup as he would when
surrounded by other Barry Bondses, and that's just plain false.

Normalizing by outs consumed does *not* correct for the interaction effect
in RC, by which a player with balanced OBP and SLG gets credit for batting
with lots of runners on base *and* for converting them efficiently, *and*
for being driven in at a very high rate.  In a real lineup, there wouldn't
be that many runners on base to convert, and the following batters wouldn't
convert the player in question as frequently, even if the player in question
put up exactly the same numbers.  RC overestimates the *marginal* value of
individual OBP and SLG, due to this self-compounding effect.

>Hmmm.  These are the major problems with MLV, as I see it:
>
>1.	(This is from my impression; if this is incorrect, please correct it.)

OK.

>	Since you use OBP and SLG, MLV undervalues walks, since walks *do*
>	move runners sometimes.

The basic RC formula (AB*OBP*SLG) undervalues walks slightly.  This could be
fixed in MLV; it's not an insurmountable obstacle.  It's also not a very large
effect, since it's extremely difficult for one player to have a noticeable
effect on the *team's* ability to advance baserunners by walks.  Since the same
formula is used for the average team, the effect mostly cancels out for the
purposes of player comparison.

>2.	MLV does not account for the effects of the running game or for a
>	player who grounds into double-plays a lot.

DPs, no.  Stolen bases can be added in as 0.3*(SB-2*CS) added to TMR.

>3.	Since you use league averages to derive MLV's, it gives no indication
>	of how much value a below average player might have.

I disagree.  It tells you how many fewer runs you will score with this guy
than you would with a league average guy.  What other measure of value did
you have in mind?

>4.	As a side effect, MLV is not well adapted to positional adjustments.
>	You rectified this somewhat, by using singular positions for players,
>	but still does not account for multi-positional players, such as
>	Tony Phillips or even Mickey Tettleton, whose value will be overly
>	high according to your adjusted MLV, since he spent a significant
>	portion of the season as a DH.

Positional value is a potential value; it's what you can get by playing the
player in question at the position in question.  Where the player *actually*
played can be prorated normally, by a weighted average of positional marginal
runs over the various positions played, by # of plate appearances.  This isn't
a problem.  In fact, I think it's more of a problem for RC, as I've said, 
since there is no baseline for RC that you can compare with on an individual
basis.

>5.	You use MLV/game as a rate of production, and this severely
>	undervalues bench players.  Mike Sharperson, for example, might get
>	only a plate appearance a game.  

You've misunderstood what MR/G is.  Nowhere do I actually use the "games
played" stat reported in the newspapers.  MR/G is what the player would be
worth playing full-time, on a per-game basis.  It's based on predicting team
PAs, assigning 1/9 of these to the player in question.  It has nothing to do
with how many games the player has actually appeared in.

>>>And I don't
>>>think that MLV will be able to derive the Thomas effect in your example
>>>correctly, either.

>>Wanna bet?  (Why don't you think so?)

>Show your work.

Oh, come on Nelson.  Instead of being petulant, how about telling where you
think it fails to account for it?  Is it the advancement value of walks that
you're worried about?  The whole point of MLV is to do the normalization that
lets you use the team RC formula to compare two individual players.  The whole
motivation for doing that was that RC/27 comparisons don't, and can't.


-- 
       David Tate        |"Out of the dugout endlessly swinging,
 dtate@unix.cis.pitt.edu | Out of the manager's throat, the sound fundamentals,
 Prof. of Story Problems | Out of the six-month season..."            
 Member ORSA, TIMS, SABR | 	Walt "Lefty" Whitman
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