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The Effect of Sportsbook Bias on Expected Profit

Sportsbooks are gambling establishments that accept bets on a variety of sports events. They are available in many countries, including the United States, and often offer bettors an online platform. They may also feature a live betting feed of current game action. The goal of a sportsbook is to maximize profits by collecting winning wagers and paying losing bettors. Despite this, sportsbooks are not without risk and should always be operated with caution.

To evaluate the magnitude of a sportsbook bias required to permit a positive expected profit to the bettor, the empirically measured CDF of the margin of victory was evaluated at offsets of 1, 2, and 3 points from the true median in each direction. The figure below shows the results of this analysis, with the height of each bar indicating the hypothetical expected profit (on a unit bet) when wagering on the team with a higher probability of winning against the spread.

In general, the optimal statistical model for sports betting is one that produces estimates of the median outcome that yield sampling distributions with the same mass on the side of the sportsbook’s proposition as the true median, and a negative probability of winning on the other. Theorem 4 is consistent with this, and it has been proven to be true by multiple investigators. In practice, it is not uncommon to find estimators that deviate significantly from the true median but still yield a positive expected profit for the bettor.