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Sunday, March 17, 2013
Joe Lemire from Sports Illustrated wrote a piece a while back detailing this very thing. He calls it baseball’s magic number but I like to look at it as the Rule of 39. [...]
Peterson asked the team’s analytics department to research the correlation of winning percentage with the number of batters faced in a game. That research, he said, found a tipping point between 38 and 39 batters faced.
—snip—
Here’s why: Since 1991 home teams that have faced fewer than 39 opposing batters in a nineinning game—four full times through the lineup, plus three additional hitters—win roughly threequarters of the time (74 percent) while teams that have faced 39 or more hitters have won only 31 percent of games.Moreover, in the last 22 seasons home teams that have faced 39 opposing hitters have won almost exactly 50 percent of their games—50.082 percent, to be more precise—making 39 the inflection point of winning or losing.

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1. jacjacatk Posted: March 17, 2013 at 09:39 AM (#4389766)NL 2012 average batters per game = 38.2
Bloody bastards.
Some of the outs wouldn't appear in that calculation of OBP because they would have come from double plays, caught stealing, pickoffs and outs on the bases immediately after a hit.
Plus sacrifice bunts which don't count against OBP
edit. And not only that, but outs on the bases mean another PA ends up on base. Of course, that can also be balanced by reaching on an error.
Of course I think this is another of those causation = correlation messes that people try to interpret as having meaning. Factor in that you can probably get similar results by looking at runs allowed and win percentage and I'm not sure this article really offers much that is new or isn't plainly obvious.
Not really comparable though, in spring training they aren't trying to win and often times are looking at just working one or two pitches. And the WBC doesn't really have the same level of competition that MLB has.
In fact I'd wager that teams have outstanding winning percentages in games in which they make fewer than 27 outs while they almost always lose when they give up fewer than 27 outs.
cfb #8 ... I think that was the point of #1 and #2. If you have allowed fewer than 38 PA per game, you have probably allowed fewer runs than average so of course the win % goes up. It would make no sense at all to use relievers more often to reduce the number of batters faced  you'd do it to reduce the number of runs scored.
Batters faced per game (or 9 innings) is of course very closely related to WHIP. AL average WHIP*9 + 27 gives 38.77 BF per 9 unadjusted for DP, CS, HBP (I think), etc. It does include SH though.
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