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Thursday, February 25, 2010
EqA renamed TAv (True Average)
Here’s Jay:
Ilya: Why is TAv better than wOBA?
Jay: 1. The fact that the stat is scaled to batting average makes it easier for the average fan to understand than wOBA being scaled to OBP. “.300 is good” is a notion with t over 100 years of baseball history behind it.
2. EqA is park adjusted, wOBA isn’t, at least as I understand it.
3. The two have virtually identical correlations to runs scored, but TAv produces a smaller RMSE. I’ll leave the defense of that statement and the grisly math to Clay Davenport, who’s got data showing that. He’ll have an article on the topic soon once he gets the PECOTA cards up, but perhaps I can get him to chime in here as well.
Me:
1. This is a feature of wOBA, not a bug. Some people prefer the BA scale and others prefer the OBP scale. That doesn’t make one “better” than the other. I can just as well show wBA by dividing by 1.15 instead of multiplying by 1.15. It’s a choice I make. It’s different, neither better nor worse.
2. wOBA as presented on Fangraphs is not park-adjusted. wOBA as presented on StatCorner.com IS park-adjusted. People can use whichever they prefer.
3. If I was interested in having the lowest RMSE at the team-level, I would come up with unacceptable weights. That’s not the point. Colin Wyers understands the point, and I hope he’s involved in trying to prove that EqA is “better’ what wOBA. At least, he’ll prove it at the game or inning level, which is where the real test should take place, not the antiquated team-level.
If you are going to call something better than wOBA, give me a chance to rebut please.
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