Judge: Statcast Exit Velocity: A statistical assessment of Park Effects

From SABR member Jonathan Judge at Baseball Prospectus on June 17, 2019:

Recently, Major League Baseball notified vendors that, beginning next season, it would shift its in-game ball tracking from the current, radar-based Trackman system to an optical-based system by Hawkeye. The impending transition makes this a good time to assess how accurately Statcast seems to be measuring balls in play, and how it has changed over time.

This series will focus on batted ball data, and particularly on two measurements made publicly available through Baseball Savant: launch speed (colloquially described as “exit velocity”) and launch angle. These are not the only batted ball measurements that Statcast captures, but these two have received the most press and arguably are the most important.

There are several drivers of batted ball launch speed and launch angle: the two most obvious are the batter (who is primarily responsible for both measurements) and the pitcher (who has some, but less effect). However, an important third input can be the stadium where the ball is struck. Ideally, there would be no such effect: one of the goals of Statcast is to overcome ballpark bias, by measuring batted ball contact at its origin before the environs can distort the outcome. And yet, this ideal is difficult to achieve: different stadiums may have different Statcast installations in different orientations in varying states of operation. Furthermore, stadiums may have inherent eccentricities that confound player efforts to give their typical performance, regardless of how they are detected by Statcast.

Read the full article here: https://www.baseballprospectus.com/news/article/50763/statcast-exit-velocity-a-statistical-assessment-of-park-effects/

Originally published: June 18, 2019. Last Updated: June 18, 2019.