Monday, September 17, 2012

Thinking Out Loud: Replacement Referees and Home-Field Advantage

Home-field advantage, like the Cubs' curse and the substandard jumping abilities of Caucasians, is one of those sports truisms that has been accepted for decades as a given. The 2011 book Scorecasting investigated this phenomenon and ventured to explain why home-field advantage still existed in the era of free agency, chartered jets, and five-star hotels. Consider this slideshow, taken from the presentation given by the authors at the 2011 Sloan Sports Analytics Conference:

In short, the authors claim that home-field advantage is explained by the psychological effects of the crowd on the officials. They claim that referees draw information from the reaction of the crowd, especially when the call is uncertain.

The replacement referees that the NFL is using give us an additional chance to test this. Given that this advantage manifests itself in uncertain, subjective calls, we expect a study to show that this effect is magnified in the presence of replacement officials, who will presumably be of worse quality than the typical NFL official and thus be uncertain about a higher number of calls.

Until the end of the referee lockout, then, I will be tracking several factors that Moskowitz and Wertheim claim demonstrate this principle clearly:
  • Penalties
  • Yards/penalties
  • Turnovers (specifically, fumble recoveries)
  • Calls overturned by instant replay
  • And, of course, home team record.
There will be a couple of caveats I'll need to pay attention to. For one, I might have to limit the overturned calls to non-scoring plays, since the NFL changed the rules this year to automatically review all scoring plays. And I'll have to make sure that there are enough regular season games played under the replacement refs to identify a statistically significant difference. Come back after the lockout ends for the update!

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