Statistics play an important role in summarizing baseball performance and evaluating players in the sport.
Since the flow of a baseball game has natural breaks to it, the sport lends itself to easy recordkeeping and statistics. Statistics have been kept for professional baseball since the creation of the American League and National League, now part of Major League Baseball.
Many statistics are also available from outside of Major League Baseball, from leagues such as the National Association and the Negro Leagues.
Contents 
The practice of keeping records of player achievements was started in the 19th century by Henry Chadwick.^{[1]} Based on his experience with cricket, Chadwick devised the predecessors to modern day statistics including batting average, runs scored, and runs allowed.
Traditionally, statistics such as batting average (the number of hits divided by the number of at bats) and earned run average (approximately the number of runs allowed by a pitcher per nine innings) have dominated attention in the statistical world of baseball. However, the recent advent of sabermetrics has created statistics drawing from a breadth of player performance measures and playing field variables. Sabermetrics and comparative statistics attempt to provide an improved measure of a player's performance and contributions to his team from year to year, frequently against a statistical performance average.
Comprehensive, historical baseball statistics were difficult for the average fan to access until 1951, when researcher Hy Turkin published The Complete Encyclopedia of Baseball. In 1969, Macmillan Publishing printed its first Baseball Encyclopedia, using a computer to compile statistics for the first time. Known as "Big Mac", the encyclopedia became the standard baseball reference until 1988, when Total Baseball was released by Warner Books using more sophisticated technology. The publication of Total Baseball led to the discovery of several "phantom ballplayers", including Lou Proctor, who did not belong in official record books and were removed.^{[2]}
Throughout much of modern baseball, several core statistics have been traditionally referenced—batting average, RBIs, and home runs. To this day, a player who leads the league in these three statistics is referred to as the "Triple Crown" winner. For pitchers, wins, ERA, and strikeouts are the most often cited traditional statistics, with a pitcher leading a league in these statistics referred to as a "Triple Crown" winner. General managers and baseball scouts have long used the major statistics, among other factors and opinions, to understand player ability. Managers, catchers and pitchers use statistics of batters against opposing teams to develop pitching strategies and set defensive positioning on the field. Managers and batters study opposing pitcher performance and motion in attempts to improve hitting.
Some sabermetric statistics have entered the mainstream baseball world that measure a batter's overall performance including Onbase plus slugging, commonly referred to as OPS. OPS adds the hitter's on base percentage (number of times reached base by any means divided by total plate appearances) to his slugging percentage (total bases divided by at bats). Some argue that the OPS formula is flawed and that more weight should be shifted towards OBP (on base percentage).^{[2]}
OPS is also useful when determining a pitcher's level of success. "Opponent Onbase Plus Slugging" (OOPS) is becoming a popular way to evaluate a pitcher's actual performance. When analyzing a pitcher's statistics, some useful categories to consider include K/9IP (strikeouts per nine innings), K/BB (strikeouts per walk), HR/9, WHIP (walks plus hits per inning pitched) and OOPS (opponent onbase plus slugging).
However, since 2001, more emphasis has been placed on DefenseIndependent Pitching Statistics, including DefenseIndependent ERA (dERA), in an attempt to evaluate a pitcher performance regardless of the strength of the defensive players behind him.
Also important are all of the above statistics in certain ingame situations. For example, a certain hitter's ability to hit lefthanded pitchers might incline a manager to provide increased opportunities to face lefthanded pitchers. Other hitters may have a history of success against a given pitcher (or vice versa), and the manager may use this information to create a favorable match up. Broadcast commentators often refer to this as "playing the percentages".
The use of performanceenhancing anabolic steroids in Major League Baseball has affected the validity of performance statistics. According to the Mitchell Report, released 13 December 2007, which concluded, in part
The illegal use of performance enhancing substances poses a serious threat to the integrity of the game. Widespread use by players of such substances unfairly disadvantages the honest athletes who refuse to use them and raises questions about the validity of baseball records.^{[3]}
Most of these terms also apply to softball. Commonly used statistics with their abbreviations are explained here. The explanations below are for quick reference and do not fully or completely define the statistic; for the strict definition, see the corresponding article for each statistic.
It is difficult to determine quantitatively what is considered to be a "good" value in a certain statistical category, and qualitative assessments may lead to arguments. It is interesting to look at recent results for some typical statistics and let readers draw their own conclusions. Using fullseason statistics available at the Official Site of Major League Baseball^{[4]} for the 2004 through 2008 seasons, the following tables show top ranges in various statistics, in alphabetical order. For each statistic, two values are given:




This article's introduction section may not adequately summarize its contents. To comply with Wikipedia's lead section guidelines, please consider expanding the lead to provide an accessible overview of the article's key points. (March 2010) 
Statistics play an important role in summarizing baseball performance and evaluating players in the sport.
Since the flow of a baseball game has natural breaks to it, the sport lends itself to easy recordkeeping and statistics. Statistics have been kept for professional baseball since the creation of the American League and National League, now part of Major League Baseball.
Many statistics are also available from outside of Major League Baseball, from leagues such as the National Association of Professional Base Ball Players and the Negro Leagues.
Contents 
The practice of keeping records of player achievements was started in the 19th century by Henry Chadwick.^{[1]} Based on his experience with cricket, Chadwick devised the predecessors to modern day statistics including batting average, runs scored, and runs allowed.
Traditionally, statistics such as batting average (the number of hits divided by the number of at bats) and earned run average (approximately the number of runs allowed by a pitcher per nine innings) have dominated attention in the statistical world of baseball. However, the recent advent of sabermetrics has created statistics drawing from a breadth of player performance measures and playing field variables. Sabermetrics and comparative statistics attempt to provide an improved measure of a player's performance and contributions to his team from year to year, frequently against a statistical performance average.
Comprehensive, historical baseball statistics were difficult for the average fan to access until 1951, when researcher Hy Turkin published The Complete Encyclopedia of Baseball. In 1969, Macmillan Publishing printed its first Baseball Encyclopedia, using a computer to compile statistics for the first time. Known as "Big Mac", the encyclopedia became the standard baseball reference until 1988, when Total Baseball was released by Warner Books using more sophisticated technology. The publication of Total Baseball led to the discovery of several "phantom ballplayers", including Lou Proctor, who did not belong in official record books and were removed.^{[2]}
Throughout much of modern baseball, several core statistics have been traditionally referenced—batting average, RBIs, and home runs. To this day, a player who leads the league in these three statistics is referred to as the "Triple Crown" winner. For pitchers, wins, ERA, and strikeouts are the most often cited traditional statistics, with a pitcher leading a league in these statistics referred to as a "Triple Crown" winner. General managers and baseball scouts have long used the major statistics, among other factors and opinions, to understand player ability. Managers, catchers and pitchers use statistics of batters against opposing teams to develop pitching strategies and set defensive positioning on the field. Managers and batters study opposing pitcher performance and motion in attempts to improve hitting.
Some sabermetric statistics have entered the mainstream baseball world that measure a batter's overall performance including Onbase plus slugging, commonly referred to as OPS. OPS adds the hitter's on base percentage (number of times reached base by any means divided by total plate appearances) to his slugging percentage (total bases divided by at bats). Some argue that the OPS formula is flawed and that more weight should be shifted towards OBP (on base percentage).^{[2]}
OPS is also useful when determining a pitcher's level of success. "Opponent Onbase Plus Slugging" (OOPS) is becoming a popular way to evaluate a pitcher's actual performance. When analyzing a pitcher's statistics, some useful categories to consider include K/9IP (strikeouts per nine innings), K/BB (strikeouts per walk), HR/9, WHIP (walks plus hits per inning pitched) and OOPS (opponent onbase plus slugging).
However, since 2001, more emphasis has been placed on DefenseIndependent Pitching Statistics, including DefenseIndependent ERA (dERA), in an attempt to evaluate a pitcher performance regardless of the strength of the defensive players behind him.
Also important are all of the above statistics in certain ingame situations. For example, a certain hitter's ability to hit lefthanded pitchers might incline a manager to provide increased opportunities to face lefthanded pitchers. Other hitters may have a history of success against a given pitcher (or vice versa), and the manager may use this information to create a favorable matchup. Broadcast commentators often refer to this as "playing the percentages".
The use of performanceenhancing anabolic steroids in Major League Baseball has affected the validity of performance statistics. According to the Mitchell Report, released 13 December 2007, which concluded, in part
The illegal use of performanceenhancing substances poses a serious threat to the integrity of the game. Widespread use by players of such substances unfairly disadvantages the honest athletes who refuse to use them and raises questions about the validity of baseball records.^{[3]}
Most of these terms also apply to softball. Commonly used statistics with their abbreviations are explained here. The explanations below are for quick reference and do not fully or completely define the statistic; for the strict definition, see the corresponding article for each statistic.
It is difficult to determine quantitatively what is considered to be a "good" value in a certain statistical category, and qualitative assessments may lead to arguments. Using fullseason statistics available at the Official Site of Major League Baseball^{[4]} for the 2004 through 2008 seasons, the following tables show top ranges in various statistics, in alphabetical order. For each statistic, two values are given:



