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Friday, December 11, 2009
wOBA Primer
Well, just a fantastic job by Alex Remington.
The only (possibly questionable) issue is when he says:
and is therefore superior to non-weighted stats like OPS and OPS+.
It is superior to OPS, no question about it. But, with OPS+, it’s more tricky. See, OPS+ also starts off with a bad weighting (approx 1.2 for OBP and 1 for SLG, when it should be 1.7 or 1.8 to 1. But, OPS+ redeems itself that it also adjusts for the park. To the extent that parks matter (Coors, PETCO, etc), then OPS+ *might* be better than wOBA. I don’t blame Alex for not getting into it, and his one line statement is mostly correct. It would be totally correct with OPS, and usually correct with OPS+.
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By the way, since Sean Forman is in charge of OPS+, any reason we can’t get him to change it to: 1.2*OBP/lgOBP + 0.8*SLG/lgSLG - 1, for OPS+? If he did that, then OPS+ would be (almost always) superior to wOBA. It gets the weights very close to wOBA, plus the added advantage of the park/league factors. Such a simple change. Listen, I have limited pull with Sean (indeed, in some cases, I have negative pull). But, if you guys speak up, he’ll listen. Write to him.