THE BAT Park Factors
Park Factors isolate the impact of the ballpark on in-game events, which can better help us predict the outcomes for players, teams, and games. While most think of parks impacting home runs, parks actually impact everything that happens on the field. Park factors are not affected by the quality of a team's hitters or pitchers. Unlike traditional park factors, THE BAT's park factors are also independent of weather, so on a 90-degree day in Atlanta, SunTrust Park would play more hitter-friendly than these factors suggest. THE BAT's park factors also account for physical properties of the parks (altitude, fence distance/height, foul ground, etc.) as well as any changes to these (such as Anaheim lowering their RF fences or Arizona adding a humidor in 2018). THE BAT's park factors use multiple years of data, account for the variance in each stat, and adjust for context.
All park factors are represented as indices with 1.00 being league average. A HR park factor of 1.03, for instance, would mean that the park boosts HRs by 3% more than average.