Officiating Bias In the NBA

Yes (unsurprisingly). Again from the MIT Sloan Sports Analytics Conference from a presentation entitled “Whistle Swallowing: Officiating & the Omission Bias.” I highlighted the most interesting stuff – so just read the bold if you are short on time.

Officiating has always been a strong point of contention in NBA circles. The flow of an NBA game can be largely influenced by the three referees on any given night. This afternoon at the Sloan Sports Analytics Conference in Boston, Tobias Moskowitz and L. Jon Wertheim presented their findings on the bias officials can exhibit in the NBA along with other sports, their study “Whistle Swallowing: Officiating & the Omission Bias”

Moskowitz and Wertheim looked at five sports in their study of omission bias which, in their words, is referees unwillingness to make incorrect calls rather than make incorrect non-calls. In their words, this bias is worse than a random mistake in officiating, which are predictable and tend to balance out over time. Omission bias however can be unknowingly and does not have the random tendencies to balance out over time. This philosophy is consistent with human psychology with the distinction people have between “doing harm” and “failing to rescue” with the latter being the much less egregious offense in many people’s eyes. The same goes for officiating.

So where does the NBA fit into this type of bias? The research showed a couple much maligned problems in the league are as big of an issue as many fans of the league would have presumed.

The first is star treatment. The study compared how likely officials were to call loose ball fouls on stars compared to non-star NBA players they were contesting in loose ball foul situations.The results were found over a 3 year study in which 1.5 million plays were examined in 3500 plus games. “Star” criteria was based on players MVP votes.

The results:

  • 42 percent of loose balls fouls called on stars in “regular” situation compared to 57 percent of the time on non-stars in plays.
  • The numbers show a much more dramatic shift, favoring the star players when they are in “foul” trouble with only 28 percent of foul calls being called on them, a huge drop from the earlier 42 percent.
  • When the roles are reversed however, and the non-star is in foul trouble, the numbers normalize again with 48 percent of the fouls called on the non-star compared to 51 percent for the star.

The other study involving the NBA involved a look at subjective calls (offensive fouls, traveling, double dribble, etc.) being made compared to non-subjective calls (kick ball, 24 second violation, etc.) over the course of the game. The tendency to want to let the players decide the game in close as well as late game situations showed itself once again in the form of omission bias, with the rate of calls falling dramatically from the 1st half to the 2nd half.Another even sharper drop in subjective calls was apparent in overtime games with the subjective or “judgment” calls. The non-subjective call rates remained very level over those time spans.

So what’s the good news about all this? It appears the omission bias in the NBA is not an isolated phenomenon. Research showed universal problems in officiating in all other sports researched including in the MLB, NHL, NFL and International Soccer.So while NBA fans may have something to complain about officiating in their sport, they can sleep a bit easier knowing that they aren’t the only ones that have to deal with the problem.


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