Log5 method

From Wiki Gonzalez

This is the name Bill James gave for a simple derivation of what is the probability that a given team A with AWin% would beat another team B with BWin%.

ProbABeatsB = (AWin% * (1 - BWin%)) / ((AWin% * (1 - BWin%)) + ((1 - AWin%) * BWin%))
            = (AWin% - (BWin% * AWin%)) / (AWin% + BWin% - (2 * AWin% * BWin%))

The simple reasoning here is you can imagine AWin and BWin as two independent random variables that get a "win" with AWin% and BWin% respectively and a "loss" with 1 - AWin% and 1 - BWin% respectively. A game in essence is comparing randomly these two random variables and saying A wins only if A picked "win" and B picked "loss" but saying A losses only when A picked "loss" and B picked "win". If A and B picked the same run again.