Tuesday, March 16, 2004

Gabriel asked how DMB could make Jamie Moyer so much worse than his success from last season would indicate. I was going to re-hash the debate from last month around defense-independent pitching stats, but decided instead to just get it straight from the horse's mouth. Below is the email I sent to Tom Trippett at Diamond Mind:

>I see that version 9 will be released soon. I was wondering if this version will take into account some of
>the recent research on balls-in-play and DIPS performed by Tom T. and Voros McCracken. I am in a DMB >simulation league where this has been a topic of some debate.

And his response:
This is about the fifth time that I've gotten this question, and I must say that I'm a little puzzled by it. It's not clear to me why there would be any impact on the DMB game itself or how we rate the players for our annual season disk.

If a pitcher, such as Tim Hudson in 2003, had a very low rate of hits allowed on balls in play, we rate him to have a low rate of hits on balls in play in our game. That's what we've always done, and I don't see any reason why this should change. I'd be surprised if your league members would want us to rate the 2003 Hudson to allow hits at the league average rate just because research suggests that extremely low in-play hit rates tend not to be repeated in the future.

This research does factor into our work in one important way. Our annual projection disk is a forecast of future performance, and we have made adjustments in how we project future performance to take this research into account. This is still a work in progress, because I think there's still more to learn about how to project future in-play hit rates, but we've already taken our first few steps down that path.

By the way, we've also added in-play batting average as a new statistic in version 9, both for real-life and simulated stats.


So there you have it, if a pitcher had good DIPS in 2003, he will stay that way in the sim, but for the projection disk, there may be some regression to the mean. Therefore, I am able to shed no light whatsoever on why Jamie isn't a good simmer, and I should just go back to deleting mortgage offers from my inbox.

Oh, and those of you with only one catcher might want to read this, from the description of version 9:

Catcher fatigue. Previously, a tired catcher would underperform at the plate but remain at full strength in the field. Now catcher fatigue affects defensive performance as well.

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