📂Sabermetrics

Definition of a Plate Appearance in Baseball

Definition ¹

The number of times a batter steps into the batter’s box and completes a turn at bat (leaving the box in any manner) is called a plate Appearance, abbreviated PA.

Theorem

• [1]: For a single batter, the plate appearances PA, at-bats AB, walks BB, hit-by-pitch HBP, sacrifice bunts SH, sacrifice flies SF, and reaches on base due to catcher’s/runner’s interference $X$ satisfy the following equation. $$ \begin{align*} PA =& AB + (BB + HBP) + (SH + SF) + X \\ 타석 =& 타수 + 사사구 + 희생타 + X \end{align*} $$
• [2]: For plate appearances PA, at-bats AB, and hits H, the following inequality holds. $$ \begin{align*} H \le AB \le PA \\ 안타 \le 타수 \le 타석 \end{align*} $$

Explanation

Sabermetrics

As a cumulative stat, the meaning that plate appearances carry is durability or diligence. When a batter who starts a game plays through it without being substituted, he usually steps into the batter’s box about 3 to 5 times; a drop in the plate appearance count in the yearly record can be seen as the batter who is supposed to produce runs doing less work, and it hints at anomalies such as a slump or an injury. Even when a player is on the roster but is used only as a pinch hitter to build up his batting feel, accumulating plate appearances is slow.

In analyzing the batting performance of an entire league, when the number of plate appearances is remarkably small, that player’s batting sample can be regarded as insufficient. For example, if a prospect A who plays for the first time in a season hits one home run in his debut game and then gets injured and sits out the rest of the season, A ends up with the bizarre record of 1 plate appearance and a slugging percentage of 4. Setting aside how unfortunate A’s baseball career is, such data should be regarded as an outlier, and appropriate measures would be necessary.

Origin

²

The batter’s box itself refers, as above, to the plate where the batter hits the baseball. The English expression Plate Appearance refers to a batter appearing at the plate, and when the batter finishes his turn at bat in any form, 1 is added. A batter who has finished his plate appearance necessarily belongs to one of the following three states.³

• He is put out.
• He reaches base and scores.
• He reaches base and is left on base.

The Difference Between Plate Appearance and At-Bat

To someone who does not know baseball well, both look like “ta-s” and are among the records that are particularly confusing. Put simply,

• a plate appearance is the number of times a person stood there regardless of the bat, and
• an at-bat is the number of times the bat physically made contact with the ball.⁴

In baseball, if you do not stand in the batter’s box there is no occasion to use the bat, so at-bats cannot be greater than plate appearances. If we call the beneficial case among those where the bat makes contact a hit, then the inequality in Theorem [2] holds. $$ 안타 \le 타수 \le 타석 $$

We know that using concrete game situations as examples to make these records understandable to a layperson confused between plate appearances and at-bats is markedly less effective. Instead, following the inequality above, we will try to understand the following records.

• (1) 4 plate appearances, 3 at-bats, 3 hits: given four chances, he seized the chance three times and contributed to the offense all three times, so it is a good record.
• (2) 5 plate appearances, 1 at-bat, 2 hits: this means at least two balls flew off a single swing. Such a record cannot exist.
• (3) 5 plate appearances, 2 at-bats, 1 hit: given five chances, he seized the chance twice and hit once among them, making the inequality hold properly.
• (3) 3 plate appearances, 0 at-bats, 0 hits: even though he was given three chances, he could not make a single at-bat and thus failed to contribute to the offense, a bad record.