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Racially biased umpires?
2007-08-14 23:46
by Bob Timmermann

After Time magazine ran with a story about a study by a University of Texas professor named Daniel Hamerhesh suggesting that home plate umpires are racially biased in ball-strike calls, Phil Birnbaum took a deeper look.

He was not too worried.

The Hammermesh study on racial bias among umpires concluded that “a given called pitch is approximately 0.34 percentage points more likely to be called a strike if the pitcher and umpire match race/ethnicity.” But I don’t think they actually say what percentage of calls are biased. I’m tried to figure this out for myself, without using regression. It depends on the assumptions you make; under the assumptions I’ll show you in a bit, I get 0.13%.

Or as Phil states at the end, about 1 in every 700 pitches.

 

Comments
2007-08-15 00:23:13
1.   xaphor
How many pitches are thrown throughout the MLB between Kemp's at bats?
2007-08-15 07:04:26
2.   Bob Timmermann
The study said the bias only applied for PITCHERS. The batter was irrelevant.

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