Thursday, April 17, 2014
Strike zone error rate
Jeff presents data that shows it's around 10% of all called pitches. Here's the quick math, based on a wrong conclusion in one of the comments:
In case someone else thinks they should add those numbers, consider this illustration. In a game of 280 pitches, you'll have 140 pitches called. Let's say there are 70 of those in the strike zone and 70 outside (all numbers for illustrative purposes only). Of the 70 in the strike zone, 7% are badly called, or 5 pitches. Of the 70 out of the strike zone, 13% are badly called, or 9 pitches.
That gives us 14 pitches out of the 140 called pitches, or 10%.
The original commenter, rather than taking a weighted average of 13% and 7% instead added them, thereby doubling the error rate. And instead of applying it to called pitches, applied it instead to all pitches, thereby doubling the quanity. And so, his estimate of 60 pitches is 4 times larger than it should be.
The lesson? Practice safe math. ?
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