Scorecasting Read Free Page B

website, mlb.com , installed cameras in ballparks to track the location of every pitch, accurate to within a centimeter, so that fans could follow games on their handhelds, pitch by pitch. The data—called Pitch f/x—track not only the location but also the speed, movement, and type of pitch. We used the data, containing nearly 2 million pitches and 1.15 million
called
pitches, for a different purpose: to evaluate the accuracy of umpires. First, the data reveal that umpires are staggeringly accurate. On average, umpires make erroneous calls only 14.4 percent of the time. That’s impressive, especially considering that the average pitch starts out at 92 mph, crosses the plate at more than 85 mph, and usually has been garnished with all sorts of spin and movement.
    But those numbers change dramatically depending on the situation. Suppose a batter is facing a two-strike count; one more called strike and he’s out. Looking at all called pitches in baseballover the last three years that are actually within the strike zone on two-strike counts (and removing full counts where there are two strikes and three balls on the batter), we observed that umpires make the correct call only 61 percent of the time. That is, umpires erroneously call these pitches balls 39 percent of the time. So on a two-strike count, umpires have more than twice their normal error rate—and in the batters’ favor.
    What about the reverse situation, when the batter has a three-ball count and the next pitch could result in a walk? Omission bias suggests that umpires will be more reluctant to call the fourth ball, which would give the batter first base. Looking at all pitches that are actually outside the strike zone, the normal error rate for an umpire is 12.2 percent. However, when there are three balls on the batter (excluding full counts), the umpire will erroneously call strikes on the same pitches 20 percent of the time.
    In other words, rather than issue a walk or strikeout, umpires seem to want to prolong the at-bat and let the players determine the outcome. They do this even if it means making an incorrect call—or, at the very least, refraining from making a call they would make under less pressured circumstances.
    The graph on this page plots the actual strike zone according to MLB rules, represented by the box outlined in black. Taking all called pitches, we plot the “empirical” strike zone based on calls the umpire is actually making in two-strike and three-ball counts. Using the Pitch f/x data, we track the location of every called pitch and define any pitch that is called a strike more than half the time to be within the empirical strike zone. The strike zone for two-strike counts is represented by the dashed lines, and for three-ball counts it is represented by the darker solid area.
    The graph shows that the umpire’s strike zone shrinks considerably when there are two strikes on the batter. Many pitches that are technically within the strike zone are not called strikes when that would result in a called third strike. Conversely, the umpire’s strike zone expands significantly when there are three balls on thebatter, going so far as to include pitches that are more than several inches outside the strike zone. To give a sense of the difference, the strike zone on three-ball counts is 93 square inches larger than the strike zone on two-strike counts. *
ACTUAL STRIKE ZONE FOR THREE-BALL VERSUS TWO-STRIKE COUNTS

    Box represents the rules-mandated strike zone. Tick marks represent a half inch.
    The omission bias should be strongest when making the right call would have a big influence on the game but missing the call would not. (Call what should be a ball a strike on a 3–0 pitch and, big deal, the count is only 3–1.) Keeping that in mind, look at the next graph. The strike zone is smallest when there are two strikes and no balls (count is 0–2) and largest when there are three balls and no strikes (count is 3–0).
ACTUAL STRIKE ZONE