BP: Studs and duds, via True Average
By looking at runs created per plate appearance, we can ID the most productive hitters
If you've followed Baseball Prospectus for any length of time, you're probably familiar with Equivalent Average, or EqA -- one of our signature hitting stats. If you're not, it's the expression of how many runs a player created per plate appearance, translated to the familiar and easy-to-understand scale of batting average.
A .260 EqA is the definition of a league-average figure; Rafael Furcal (.262) and Stephen Drew (.259) were both right around that mark. A .230 mark is replacement-level -- the caliber of what a waiver-wire pickup or a Triple-A player could provide; a team has almost nothing to lose by trying something different than a player at this level. Note that the Colorado Rockies' Garrett Atkins (.230) and the Florida Marlins' Emilio Bonifacio (.228) both lost their starting jobs last year.
There's a lot involved in turning hits, walks, total bases, stolen bases, caught stealing and other data into this batting-average-like form. We even build park and league adjustments into the formula, so a .300 EqA in hitter-friendly Coors Field has the same impact on scoring as it does in pitcher-friendly Petco Park -- and a .300 today has the same impact as it did in the low-scoring 1960s or the high-scoring 1930s. It's all worthwhile, because EqA does a much better job of predicting scoring levels than batting average, on-base percentage, slugging percentage, OPS (on-base plus slugging), OPS+ and more complicated run estimators.
This spring, BP chose to rebrand EqA as True Average (abbreviated TAv). Why? Because we feel strongly that the new name underscores our ability to get a "truer" grasp on the quality of a hitter than the aforementioned traditional or more modern stats do. We're hopeful that this simple, easy-to-remember name can reach a wider audience.
The best way for those unacquainted to understand True Average is to look at several examples using our 2010 PECOTA hitter projections. Below are five players whose True Averages are higher than you might expect given their batting averages, OBPs, SLGs and other stats -- and five whose True Averages are lower.
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