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Apr 26 '14
Umpires and expectation bias.
New data on how often umpires make bad calls — and what correlates with them — reveals a social psychological phenomenon called “expectation bias”:
- Umpires gave a slight edge to the home team pitchers, calling 13.3% of their pitches outside the zone as strikes. Visitors got 12.6%.
- The count mattered: At 0-0, the error rate was 14.7%, at 3-0, 18.6% of pitches outside the zone were called as strikes, and at 0-2, only 7.3% of pitches outside the zone were called as strikes.
- All-star pitchers were more likely than others to get favorable calls…
- …especially if the pitcher had a reputation as a location pitcher.
- The importance of the situation (tie game, bottom of the ninth) made no difference in bad calls.
It seems that expectation accounts for a lot of these findings. It’s not that what you see is what you get. It’s that what you expect is what you see.
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