Pythagorean Expectation

Pythagorean expectation is a formula invented by Bill James to estimate how many games a baseball team "should" have won based on the number of runs they scored and allowed. Comparing a team's actual and Pythagorean winning percentage can be used to evaluate how lucky that team was (by examining the variation between the two winning percentages). The name comes from the formula's resemblance to the Pythagorean theorem.

The basic formula is:

where Win is the winning ratio generated by the formula. The expected number of wins would be the expected winning ratio multiplied by the number of games played.

Read more about Pythagorean Expectation:  Empirical Origin, "Second-order" and "third-order" Wins, Theoretical Explanation, Use in Basketball, Use in Pro Football

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