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Wednesday, January 31, 2007
Is Vladimir Streaky?
“He’s on the slide,” said one scout. “He’s turned into much more of a streak hitter than he used to be. It used to be that if you tried to pitch him inside and you didn’t bury the ball inside, he’d hit it good. Now you can get away with a little more, and I think it’s because there are days when his back doesn’t feel so good. He seems to go through periods where any tweak in his back affects his swing.”
Is this true? Here’s what I did:
I start with his gamelogs, and did two calculations: one was his linear weights, and another was simply marking the game as “good, typical, bad” (22% of the games were good and 21% were bad). I then looked at the average score of his next 5 games. What did I find?
This is his best 5-game streak and this was his worst. (Thank you Sean Forman!)
The standard deviation of all his next-5-game LWTS was 0.44 runs. Is that typical? Darned if I know. His next-5 game “good, typical, bad” was 0.296. Is that typical? If he was not streaky, if all his performances were random, we would have expected a standard deviation of 0.293. So, we have some evidence here that Vlad is not streaky any more than any other hitter.
Another way to test it is to simply throw all his games into a bucket, and pick them out one at a time. For example, the first six games of this random season are: 86, 91, 155, 151, 85.... . The standard deviation of the next-5-game LWTS was 0.43 runs, and the next 5-game “good, typical, bad” was 0.29 units. If I redo the exercise, I get: 0.44 runs, 0.28 units. Another random ordering gives me: 0.40, 0.30. And another gives me: 0.37, 0.28.
You bored too? Yeah, me too.
Let me try a 10-game streak instead. Our expected random standard deviation of “good, typical, bad” is .207 units. Vlad’s actual is .227 units, a bit streakier than expected.
What if I repeat the random game exercise? I ran the exercise 100 times, and he exceeded the .227 level 18 times. That is, 18% of the time, we expect Vlad’s streakiness to have a level of .227 or higher, just by luck.
Seems to me that Vlad is as streaky as any other player.