Log 5 is a formula invented by Bill James to estimate the probability that team A will win a game, based on the true winning percentage of Team A and Team B. It is equivalent to the Bradley-Terry-Luce model used for paired comparisons, the Elo rating system used in chess, and the Rasch model used in the analysis of categorical data. Let be the fraction of games won by team and also let be the fraction of games lost by team . The Log5 estimate for the probability of A defeating B is . A few notable properties exist: It may also be conveniently rewritten using the odds ratio as Here as before .