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Thursday, May 19, 2011
Small sample size BABIP
First you have to understand that I love Jered Weaver. He’s a great pitcher. I thought the biggest injustice in the Cy Young voting is how he was an after-thought when he should have been one step behind Felix Hernandez. It’s why I don’t think that Felix’s win was such a saber-revelation, since Felix won it based on ERA and IP and K. Weaver was a step behind Felix overall. If Felix did not pitch in 2010, the saber case would have fallen strongly on Weaver (also had the same 13-12 record). And he finished in the Cy Young race, as if sabermetrics had just a small impact.
On April 29, 2011, I wandered over to HalosHeaven to see what they were talking about with regards to Jered Weaver, and his fantastic start. His BABIP was exceptionally low, much below his career .280. But, someone there thought he reached some new level of talent. I asked him to give me an over/under line for rest of season, and he proposed .265. I of course took the over. (At least he didn’t propose something ridiculously low. Proposing .265 is still pretty low, but not obscenely low.)
In the four start since I made my post, his BABIP is .305.
This is really how you sell people on this. You make them bet on it. They have to have a vested interest, where they are going to follow the situation.
It’s not like we saberists just decided to believe that a low BABIP is unsustainable. We studied the issue. We relied on actual past performance. We relied on the data that the players themselves produced. All we are saying is: here, take a look at the weight of history, and before you decide to bet against what’s always happened, YOU tell us why this time, it’s “different”. Because I can guarantee you, everyone thinks their particular case is different, when in reality, you are going to lose far more than you are going to win if you bet on your insights. Indeed, it’s not even your insight, but on your interpretation of the numbers you see.
Had the person made the bet based on a change in Jered Weaver’s mechanics or approach, that would be one thing. But the way it always works is that everyone understands numbers enough to be dangerous.
Saberists are the Amazing Randis to the Uri Gellers out there.
And come next April, and for every April until the day I die, there will always be someone who will have a BABIP of .220 after his first 6 starts, and a very small percentage of them will sustain anything close to that for the rest of the season. And in none of those situations should you make an even (50/50) bet.