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Baseball Hacks by Joseph Adler

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Measure Pitching with DIPS

Measure a pitcher’s performance independent of the fielders’ performance using DIPS.

In December 1999, baseball fan Voros McCracken came up with a new method of measuring pitching. McCracken started to wonder whether a pitcher could really do anything about balls in play; were outs from balls in play a function of a pitcher’s skill, the defense’s skill, or dumb luck? He set out to test this hypothesis and discovered (much to his surprise) that it wasn’t pitcher skill. He concluded that what happens after a ball is put in play depends on the defense. Only on walks, strikeouts, and home runs is the defense not involved.

To help measure a pitcher’s performance independent of the fielders’ performance, McCracken came up with a system he called defensive independent pitching stats (DIPS). If you want to know more about the story behind this formula, Michael Lewis’s book Moneyball has a nice write-up on Voros McCracken. If you want to learn how the formula works, read on.

The Formula

The formula for DIPS is, unfortunately, a little complicated. See the sample code that follows for an explanation of DIPS calculations. I’ll just launch into the code to explain how to calculate this measurement. (I used Voros McCracken’s own explanation for DIPS 2.0 numbers to make the following calculations.)

The process proceeds in two phases. First, a set of defense-independent measurements are calculated: DIPS intentional walks allowed (dIBB), DIPS hit batsmen (dHP), DIPS total ...

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