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April 14, 2005

Crooked Numbers

Sizing Up Small Sample Size

by James Click

Every year is a fresh start. For teams and for players the changes of a winter's worth of work are finally on display. Despite all the changes from last year, most of baseball remains the same from year to year, but there is an adjustment period in the early part of the season as teams and players settle into the season.

Small sample size doesn't mean no sample. While there's meaning in how a team starts off, it's also important to determine whether the early parts of the season can be deceptive for reasons other than the lack of sufficient data, especially when considering individual player performances. There's already evidence that hitters tend to perform better in the first half of the season than in the second half. There's the conventional wisdom that pitchers dominate in the colder months early in the season while August is when the bats wake up. Then there are the A's fans who keep looking at Barry Zito's 4.51 ERA the last three Aprils followed by five months of 2.74, 3.80, 3.46, 3.13, and 3.34.

April results that don't fit the public perception are usually attributed to some change discovered by the media looking for the cause. A hot start by a hitter is attributed to a change in batting stance, weight, or physique. This year's example is Eric Hinske whose new stance is the easy answer to his hot start. With pitchers, learning or mastering a new pitch or changing the delivery are the easy answers for early success. Teams off to hot starts have new veteran leadership or youthful exuberance.

Inherent in a lot of this discussion is the idea that other players have yet to adjust to the changes in their opponents. In the matchup of batter and pitcher, we usually assume that the pitcher benefits more from deception and lack of information than the hitter. Pitchers never before seen by hitters can hide the ball in different ways, mix in unexpected pitches, and throw off a hitter's timing with a new windup. Warren Spahn put it best: "Hitting is timing; pitching is upsetting timing."

One quick way to determine if pitchers see an early season advantage is to look at league wide stats broken down by month: