Everything you always wanted to know about: WPA - Big League Stew - MLB Blog - Yahoo! Sports

Everything you always wanted to know about: WPA - Big League Stew - MLB Blog - Yahoo! Sports:

"What it stands for: Win Probability Added. As Hardball Times's Dave Studeman has written, it's gone by a lot of different names. 'Player Win Averages,' 'Player Game Percentage,' 'Win Expectancy,' 'Player's Win Value,' etc. But WPA is the the most common name for it these days.

How they calculate WPA: Though the arithmetic can be a mother, Win Probability Added is one of the easiest of all the advanced stats to explain. Put simply, it's a measure of how much any game event contributes to the eventual outcome of the game, win or loss."