THE BOOK--Playing The Percentages In Baseball

Monday, August 25, 2008

Long and short atbats

Similar to my “Fixing VORP” blog post, treat this post as a “Sabermetric Announcements of Public Service” (with the unfortunate acronym of SAPS).  John Dewan talks about long and short atbats, and the profile report is now part of Bill James’ site, to which I replied:

John, Bill:

I’m not sure that your readers appreciate the bias in the long and short AB data.  What an AB of 1-pitch represents is: “What happens when the player makes contact on the first pitch” (*).

If the batter swings and misses at the first pitch, it does not count toward the 1-pitch data, and instead will now be part of the 2-pitch data.  (Similarly, a called ball on the first pitch will remove it from the 1-pitch data.)

As the league data shows on the 1-pitch at bat (very high) it makes it seem like everyone should be swinging on the first pitch.  But, the data itself is the *result* not the *approach*.

If on the other hand you asked: “What happens when the batter swings at the first pitch”, you will get different data, because now this will include the swing&miss.

You guys are probably aware of all this.  But, seeing posts on outside forums, and lots of readers simply are not thinking of it in those terms.

You might like this chart:
http://tangotiger.net/halejon/allcounts.html

And, Linear Weights by the Pitch Count provides a great basis for figuring out the pitch count approach.  But, that’s topic for another discussion.

(*) Foul balls that are not caught provide a tiny wrinkle to my statement.  The general idea holds.

Tom