
In baseball, wRAA (weighted Runs Above Average) measures the number of runs a player contributes to his team relative to a league average player. Spectator’s algorithm assigns a weight to each offensive event based on the number of runs that event is expected to produce. So, while hitting a single with no men on base does not score a run, that single will statistically return an expected fraction of a run. That value, and the expected point values of every offensive event, become weights in the wRAA formula into which player data are fed.