Equivalent Average (EqA) is a
baseball
Baseball is a bat-and-ball sport played between two teams of nine players each, taking turns batting and fielding. The game occurs over the course of several plays, with each play generally beginning when a player on the fielding tea ...
metric invented by
Clay Davenport
Clay Davenport is a baseball sabermetrician who co-founded Baseball Prospectus (BP) in 1996. He co-edited several of the ''Baseball Prospectus'' annual volumes and is a writer for BaseballProspectus.com. Much of his work for BP was behind the sce ...
and intended to express the production of hitters in a context independent of park and league effects. It represents a hitter's productivity using the same scale as
batting average
Batting average is a statistic in cricket, baseball, and softball that measures the performance of batters. The development of the baseball statistic was influenced by the cricket statistic.
Cricket
In cricket, a player's batting average is ...
. Thus, a hitter with an EqA over .300 is a very good hitter, while a hitter with an EqA of .220 or below is poor. An EqA of .260 is defined as league average.
The date EqA was invented cannot readily be documented, but references to it were being offered on the rec.sport.baseball
usenet
Usenet () is a worldwide distributed discussion system available on computers. It was developed from the general-purpose Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Ellis conceived the idea in 1979, and it was ...
group as early as January 14, 1996. Baseball Prospectus renamed it True Average (TAv) in 2010, in an attempt to make it more accessible.
Definition and rationale
In the formula given in the box above, the abbreviations are: H=Hit, TB=Total bases, BB=Bases on balls (walks), HBP=Hit by pitch, SB=Stolen base, SH=Sacrifice hit (typically, sacrifice bunt), SF=Sacrifice fly, AB=At bat, CS=Caught stealing.
EqA is one of several
sabermetric
Sabermetrics, or originally SABRmetrics, is the empirical analysis of baseball, especially baseball statistics that measure in-game activity. Sabermetricians collect and summarize the relevant data from this in-game activity to answer specific ques ...
approaches which validated the notion that
minor league
Minor leagues are professional sports leagues which are not regarded as the premier leagues in those sports. Minor league teams tend to play in smaller, less elaborate venues, often competing in smaller cities/markets. This term is used in Nor ...
hitting statistics can be useful measurements of
Major League ability. It does this by adjusting a player's raw statistics for park and league effects.
For instance, the
Pacific Coast League
The Pacific Coast League (PCL) is a Minor League Baseball league that operates in the Western United States. Along with the International League, it is one of two leagues playing at the Triple-A (baseball), Triple-A level, which is one grade bel ...
is a minor league known to be a very friendly venue for hitters. Therefore, a hitter in the PCL may have notably depressed raw statistics (a lower batting average, fewer
home run
In baseball, a home run (abbreviated HR) is scored when the ball is hit in such a way that the batter is able to circle the bases and reach home plate safely in one play without any errors being committed by the defensive team. A home run i ...
s, etc.) if he were hitting in another league at the same level. Additionally, in general the level of competition at the PCL is lower than that in the Majors, so a hitter in the PCL would likely have lesser raw statistics in the Majors. EqA is thus useful to strip certain illusions from the surface of players' raw statistics.
EqA is a derivative of Raw EqA, or REqA. REqA is (H + TB + 1.5*(BB + HBP + SB) + SH + SF) divided by (AB + BB + HBP + SH + SF + CS + SB). REqA in turn is adjusted to account for league difficulty and scale to create EqA.
EqA has been used for several years by the authors of the ''
Baseball Prospectus
Baseball Prospectus (BP) is an organization that publishes a website, BaseballProspectus.com, devoted to the sabermetric analysis of baseball. BP has a staff of regular columnists and provides advanced statistics as well as player and team perf ...
''. It is also one of the statistics predicted for each hitter in Baseball Prospectus's annual
PECOTA PECOTA, an acronym for ''Player Empirical Comparison and Optimization Test Algorithm'', is a sabermetric system for forecasting Major League Baseball player performance. The word is a backronym based on the name of journeyman major league player Bil ...
forecasts.
EqA is scaled like a batting average, which is the number of safe hits divided by the number of official at bats. However, Davenport EqA aims to capture not so much hits per at bat but instead "runs produced per at bat".
[For this interpretation see Clay Davenport, "Davenport Translations Q & A," ''Baseball Prospectus 2000'', C. Kahrl, C. Davenport, J.S. Sheehan, and R. Jazayerli, Eds., (Washington, D.C.: Brassey's Sports, 2000): 3-6.] In that sense, EqA is akin to a larger family of run estimators that sabermetricians use.
See also
*
Total player rating
*
Value over replacement player
In baseball, value over replacement player (or VORP) is a statistic popularized by Keith Woolner that demonstrates how much a hitter or pitcher contributes to their team in comparison to a replacement-level player who is an average fielder at that ...
*
Win shares
References
{{reflist
External links
"The Book" Blog Commentary on EqA
Batting statistics