Expected Weighted On-base Average (xwOBA): xwOBA is formulated using exit velocity, launch angle and, on certain types of batted balls, Sprint Speed. In the same way that each batted ball is assigned an xBA, every batted ball is given a single, double, triple and home run probability based on the results of comparable batted balls since Statcast was implemented Major League wide in 2015. xwOBA also factors in real-world walk and strikeout numbers, and is reported on the wOBA scale. By comparing expected numbers to real-world outcomes over a period of time, it can be possible to identify which hitters (or pitchers) are over- or under-performing their demonstrated skill.