Equivalent Average is a baseball

Baseball

Baseball is a bat-and-ball sport played between two teams of nine players each. The aim is to score runs by hitting a thrown ball with a bat and touching a series of four bases arranged at the corners of a ninety-foot diamond...

 metric invented by Clay Davenport

Clay Davenport

Clay Davenport, a native of Hampton Roads, Virginia, now living in Baltimore, Maryland, is a baseball sabermetrician who co-founded Baseball Prospectus in 1996. He co-edited several of the Baseball Prospectus annual volumes and is a writer for BaseballProspectus.com...

 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

Batting average is a statistic in both cricket and baseball that measures the performance of cricket batsmen and baseball hitters. The two statistics are related in that baseball averages are directly descended from the concept of cricket averages.- Cricket :...

. 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.

When EqA was invented cannot readily be documented, but references to it were being offered on the rec.sport.baseball usenet

Usenet

Usenet is a worldwide distributed Internet discussion system. It developed from the general purpose UUCP architecture of the same name.Duke University graduate students Tom Truscott and Jim Ellis conceived the idea in 1979 and it was established in 1980...

 group as early as January 14, 1996.

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

Sabermetrics is the specialized analysis of baseball through objective, empirical evidence, specifically baseball statistics that measure in-game activity. The term is derived from the acronym SABR, which stands for the Society for American Baseball Research...

 approaches which validated the notion that minor league

Minor league baseball

Minor league baseball is a hierarchy of professional baseball leagues in the Americas that compete at levels below Major League Baseball and provide opportunities for player development. All of the minor leagues are operated as independent businesses...

 hitting statistics can be useful measurements of Major League

Major League Baseball

Major League Baseball is the highest level of professional baseball in the United States and Canada, consisting of teams that play in the National League and the American League...

 ability. It does this by adjusting a player's raw statistics for park and league effects.

For instance, the Pacific Coast League

Pacific Coast League

The Pacific Coast League is a minor-league baseball league operating in the Western, Midwestern and Southeastern United States. Along with the International League and the Mexican League, it is one of three leagues playing at the Triple-A level, which is one step below Major League Baseball.The...

 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

Home run

In baseball, a home run is scored when the ball is hit in such a way that the batter is able to reach home safely in one play without any errors being committed by the defensive team in the process...

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

Baseball Prospectus 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 player and team performance projections on the site...

. It is also one of the statistics predicted for each hitter in Baseball Prospectus's annual PECOTA

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 Bill Pecota, who with a lifetime batting average of .249...

 forecasts.

EqA is scaled like a batting average, which is the number of safe hits divided by the number of plate appearances. However, Davenport EqA aims to capture not so much hits per at bat but instead "runs produced per at bat". In that sense, EqA is akin to a larger family of run estimators that sabermetricians use.

Renaming

In 2010 Baseball Prospectus renamed EqA "True Average" (abbreviated TAv). The rationale is that "the new name underscores our ability to get a 'True-r' grasp on the quality of a hitter than the aforementioned traditional or more modern stats do. Quite frankly, we're hopeful that this simple, easy-to-remember name can reach a wider audience."

External links

• Clay Davenport
  Clay Davenport
  Clay Davenport, a native of Hampton Roads, Virginia, now living in Baltimore, Maryland, is a baseball sabermetrician who co-founded Baseball Prospectus in 1996. He co-edited several of the Baseball Prospectus annual volumes and is a writer for BaseballProspectus.com...
  
  , "Baseball Prospectus Basics: About EqA," BaseballProspectus.com (February 24, 2004).
• "The Book" Blog Commentary on EqA