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RC/25 Introduction (Preliminary Final)
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More options Nov 3 2012, 11:20 am
Newsgroups: rec.sport.baseball, rec.sport.baseball.data
Followup-To: rec.sport.baseball
From: n...@Xenon.Stanford.EDU (Nelson Lu)
Date: Sat, 3 Nov 2012 08:20:29 -0700 (PDT)
Local: Sat, Nov 3 2012 11:20 am
Subject: RC/25 Introduction (Preliminary Final)
(It's taken a while -- various things have tied me up -- but here they are...)

The following posts list major league teams' regular position players' RC/25 by
position.  Here are a bit of definitions:

RC/25:

A stat created by Bill James to measure how many runs a lineup of 9
of the same individual would score in a game.  (The "real" version is RC/27,
since there are 27 outs in a game; however, since certain stats are not readily
available to us during the season, James has an abbreviated version known as
RC/25 to adjust for the absence of those stats.  For the formula to RC/27,
please e-mail me.  It is also available in Total Baseball and many other
reference manuals.)

A = H + BB - CS
B = 1.125 * 1B + 1.69 * 2B + 3.02 * 3B + 3.73 * HR + .29 * BB
+ .492 * SB - .04 * SO
(Formerly B = TB + .64 * SB + .24 * BB - .03 * K)
C = AB + BB

RC = ((A + (2.4 * C)) * (B + (3 * C)) / (9 * C)) - (.9 * C)
O = AB - H + CS
RC/25 = RC / O * 25

(The reason why HBP, among other stats, is not included is not because I think
that they're not important; it's that the data sources I use do not include
them with the "primary stats," and therefore, adding HBP and other stats would
effectively require twice the work, and the gain, while considerable, was
judged by me to be not worth it in interim reports.)

There are three additional Bill James adjustments that I do not use:

1.      He adjusts for BA with runners on base.  Originally, the adjustment was
not published; but it has been, in the most recent STATS Major League
Handbook and other sources.  I am, however, not incorporating this
change since I have found this change to be arbitrary and also
increasing team-dependence.

2.      He also adds additional points for a non-bases empty HR.  Again, this
is highly arbitrary -- why not add points for a non-bases loaded
1B, 2B, or 3B?  Further, this increases team-dependence as well, which
reduces the usefulness of RC.

3.      He then adds up all players' RC on a team and adjusts it in a factor
that is based on whether the team scored more than it is expected or
less.  I find that this defeats the point of RC, so I do not use this

PRC/25:

Park-adjusted RC/25.  Park adjustment is a topic that I don't know how
to explain well in a paragraph, so I will not attempt to try.  However, many
works that explain it are available on the net, and any search engine should
yield a number of useful articles.  For these numbers, only this year's park
factors are used.

Value:

An estimate of how many runs a player is above the ever so elusive
"replacement level" (that is, a level of performance at which a player can
easily be found at little or no cost to a team).  For these posts, replacement
level is estimated at 50 points of OBP and 50 points of SLG below the average
for each position.

Notes:

1.      For these posts, the players who were traded during the middle of the
season have their park factors prorated by AB + BB with the teams.
(This is not mathematically correct, but is the best I can do for now.)
2.      Please send to me corrections if I misplaced someone's position.

evidence." - Bill James (thanks, Bill Reich)
=========================================================================== ====
GO (LOS ANGELES) ANGELS OF ANAHEIM!
=========================================================================== ====
Nelson Lu (n...@cs.stanford.edu)