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April 8, 2005

Averages and Extremes

Gleaning Information from Performance Spikes

by Michael Rawdon

Batting Average gets no love anymore.

Three decades of sabermetric analysis has diminished the once-proud Triple Crown stat through bites (on-base percentage) and nibbles (batting average on balls in play). It's enough to drive any self-respecting free-swinger to distraction.

But batting average is important. In 2004, hits accounted for more than 70% of the on-base events in on-base percentage across the majors. The first base of each hit accounted for more than 60% of total bases in the majors, a key to slugging average. A single is more valuable than a walk, because it carries runner-advancement potential the walk mostly lacks.

So a better understanding of batting average seems like useful knowledge to have.

Batting average is a skill. Being able to choose to swing at a ball, put it in play and successfully reach first base before being thrown out is an ability which some players possess at higher level than others. Of course, it's also a famously volatile stat. Being a skill, if in a single season a player shows a large deviation from his previously-established level of hitting, then you'd expect that the next year he'd likely see a regression to that established level, wouldn't you?

This was the theory behind my analysis of Pat Burrell's poor 2003 season. In that, I used constraints of looking only at players who saw a big drop in batting average while their patience and isolated power remained about the same. Why not look at a much larger pool of players, without that constraint, and see how they performed?