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Monday, March 17, 2008
Where did FIP come from?
Originally, FIP was simply a linear regression of Voros’ more complicated system. It correlated at r=.99 or some high number. Later on, I ended up figuring out privately what Kevin Harlow did publicly. And Tom Tippett in a throwaway line essentially confirmed the same thing (go all the way to the bottom, and page up a little bit):
Clemens struck out 1355 more batters, but if he hadn’t, some of those batters would have reached base, and some would have been retired in other ways. If his strikeout rate had been at the league average, it’s possible that he would have allowed another 125 walks, 35 homers, and 320 more hits on balls in play. Using Palmer’s run values and reasonable assumptions about the distribution of those hits among singles, doubles, and triples, those strikeouts are worth about 250-280 runs.
And 2710/1355 = 0.20 runs. Hopefully, the derivation by Kevin and Tom is enough to explain the basis of FIP.