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RATING SPORTS TEAMS

Most gamblers believe that when bookies set point spreads their goal is to have half the money bet on each team. If I bet $10, for example, on a 7.5-point favorite to cover the spread, I win $10 if the team covers but I lose $11 if the favorite does not cover. If the favorite covers the points spread half the time, on average each $10 bet results in an expected profit of (1/2)($10) + (1/2)(−$11) = $−.50. Thus a bettor loses on average $0.50/ $10.50 or $1/21 per dollar bet. Assuming we bet the same amount on each game, to break even we would have to win a fraction p of our bets where p(10) + (1 − p)(−11) = 0. The value p = 11/21 = .524 solves this equation. Thus to win money on average we must beat the point spread at ...

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