The Origins of Log5October 3, 2010 Posted by Sobchak in Log5 Of
all Bill James’ sabermetric innovations, my favorite has always
been the log5 formula for determining matchup probabilities. It
provides a method for taking the strengths of two teams and
estimating the probability of one team beating the other. It can
also be applied to individual player matchups, such as a batter
facing a pitcher. Here is a common way to express the formula
for the context of team matchups: Unfortunately this formulation
doesn’t shed much light on why James called this log5, or where
the formula came from in the first place. James’ Original
Formulation James introduced the formula in the 1981 Baseball
Abstract, which is excerpted here. In his initial presentation,
James first converted each team’s winning percentage (or , their
probability of success) into what he called their . Solving for
: After this conversion, the formula is simple: Logarithms,
Odds, and Odds Ratios So where does the “log” in log5 come from?
I’m not sure e