The NBA study of referee bias

As a response to Justin Wolfers and Joseph Price, the NBA financed a study supposedly showing there is no racial bias in refereeing.  Here is a WSJ analysis of that study.  Here is part of what they found:

Columbia University statistician Andrew Gelman, who has blogged
about the Wolfers-Price study and participated in a conference call
with Segal and me, said, “What the statistics tell you is that there’s
a pattern in the data that’s not explainable by chance.” University of
California-Irvine statistician Hal Stern told me the NBA’s study “can’t
be said to disprove the Price-Wolfers analysis.”

the NBA’s study didn’t include players who weren’t called for any
fouls, making Segal’s results “suspect,” according to Mr. Gelman. Mr.
Fluhr responded, “I’m not sure if you’re looking at non-calls, it would
affect the data.” He added that Segal had the data necessary to
incorporate such players, but didn’t consider the data relevant,
instead only focusing on foul calls. Messrs. Wolfers and Price included
all players who appeared in the games they examined.

The NBA does promise to examine non-calls and redo some of the results.  I do not think we have yet gotten to the bottom of this, but my "haven’t read anything but the initial study" intuition (and Steve Levitt’s comments; see also Voxbaby) is that the result of bias will hold up.

Thanks to Chris Masse for the pointer.

Addendum: Wolfers claims the NBA study supports his results.


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