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Tuesday, September 20, 2011
UZR yapfest
Fangraphs posted an article on UZR, which they subsequently pulled, due to inaccuracies in statements. That led to a post explaining why they did it. Anyway, I put in my two cents (which I’ll repost below the fold). And there’s also alot of UZR discussion that is now taking place at this new thread. Some good stuff, if somewhat disjointed.
My UZR contributions:
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“- not assessing the starting position of a player”
UZR takes the position that the starting spot of a player is a skill. And it assigns it to the player.
You can agree or disagree. But, it’s not a bias. It’s a feature, insofar as UZR sees it.
And yes, there are random biases (which are solved by larger sample size) and systematic biases (which are exacerbated by larger sample size) to recording data.
There’s also random and systematic biases to the “eye test”.
Pick your poison.
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Otherwise, what’s the alternative? Your own personal smushing system? Is that somehow going to give you more confidence than fWAR?
And if you don’t like UZR, just replace it with whatever you’d use in your smushing system.
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(The measurement error for those not following is that we don’t know how many opportunities Tulo actually has in any given year, nor the “quality” of those opportunities. While we can figure out on the batting side what kind of opps he has, facing Halladay, facing Lee, etc, we have a problem figuring out what kind of chance Tulo has on any ball in play. So, we ESTIMATE each and every single ball in play and say, “ok, that one had a 90% chance of making an out, and that one had a 20% chance”. But, we don’t REALLY know that it was 90%. It could have been 80% or 95%. It’s a huge difference. Unlike batter v pitcher where if you face Halladay, you know, plus or minus 1%, the chance of getting on base against Halladay. Measurement error, if random, is of course “solved” by sample size. If systematic, it’s actually made worse by sample size.)
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My yapfest contribution:
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