The practice was started by Henry Chadwick in the 19th century who devised the concepts of batting average and earned run average based on his experience of cricket. Statistics have been kept for the Major Leagues since their creation.
General managers and baseball scouts study player statistics to decide what players to try to get for their team. Managers, catchers and pitchers study statistics of batters on opposing teams to figure out how best to pitch to them and position the players. Managers and batters study opposing pitchers to figure out how best to hit them. Managers often base their personnel decisions during the game on statistics, such as choosing who to put in the lineup, or which relief pitcher to bring in.
Traditionally, statistics like batting average for batters (the number of hits divided by the number of at bats) and earned run average (approximately the number of runs given up by a pitcher per nine innings) have governed the statistical world of baseball. However, the advent of sabermetrics brought an onslaught of new statistics that better gauge a player's performance and contributions to his team from year to year.
Some sabermetrics have entered the mainstream baseball statistic world. On-base plus slugging (OPS) is a somewhat complicated formula that gauges a hitter's performance better than batting average. It combines the hitter's on base percentage ([hits + walks + number of times hit by pitches] divided by [number of times at bat + walks + number of times hit by a pitch + number of sacrifice flies]) with their slugging percentage (total bases divided by at bats). Walks plus hits per inning pitched (or WHIP) gives a good representation of a pitcher's abilities; it is calculated exactly as its name suggests.
Also important are all of those statistics in certain in-game situations. For example, a certain hitter's ability to hit left-handed pitchers might cause his manager to give him more chances to face lefties. Other hitters may have a history of success against a given pitcher (or vice versa), and the manager may use this information to engineer a favourable matchup.
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 stats for the first time. "Big Mac" became the standard baseball reference until 1988, when Total Baseball was released by Warner Books, using even more sophisticated technology. (This led to discovery, and expulsion, of several players who didn't belong in the record books -- "phantom ballplayers", like Lou Proctor.)
Commonly used statistics
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.
- 1B - Single - hits on which batters only reached first base safely
- 2B - Double - hits on which batters only reached second base safely
- 3B - Triple - hits on which batters only reached third base safely
- AB - At bat - Batting appearances, not including bases on balls, hit by pitch, sacrifices, interference, or obstruction
- BA - Batting average (also abbreviated AVG) - hits divided by at bats
- BB - Base on balls (also called a "walk") - times receiving four balls and advancing to first base
- BB/SO - Walk-to-strikeout ratio - number of base on balls divided by number of strikeouts
- EBH - Extra base hit (Sometimes EB or XBH) - doubles plus triples plus home runs
- FC - Fielder's choice - times reaching base when a fielder chose to try for an out on another runner
- G/F - Ground ball fly ball ratio - number of ground balls divided by number of fly balls
- GIDP - Ground into Double play - number of ground balls hit that became double plays
- H - Hit - times reached base because of a batted, fair ball without error by the defense
- HBP - Hit by pitch - times touched by a pitch and awarded first base as a result
- HR - Home run - hits on which the batter successfully touched all four bases, scoring a run and batting in between one and four runs (a home run with four runs batted in – i.e. bases loaded – is a grand slam).
- LOB - Left on base - number of runners not out nor scored at the end of an innning.
- OBP - On base percentage - times reached base (H + BB + HBP + FC) divided by plate appearances
- OPS - On-base plus slugging - on-base percentage plus slugging percentage
- PA - Plate appearance - number of completed batting appearances no matter the result
- RBI - Run batted in - number of runners who scored due to a batters's action, except when batter grounded into double play or reached on an error
- SAC - Sacrifice bunt - number of times bunts advanced other runners (someitmes called sacrifice hit or SH)
- SF - Sacrifice fly - number of fly ball outs which allow another runner to score
- SLG - Slugging percentage - total bases divided by at-bats
- SO - Strike out (also abbreviated K) - number of times that strike three is taken or swung at and missed, or bunted foul
- TB - Total bases - one for each single, two for each double, three for each triple, and four for each home run
- TOB - Times on base - times reaching base as a result of hits, walks and hit by pitches
- CS - Caught stealing - times tagged out when attempting to steal a base or when picked off
- SB - Stolen base - number of bases advanced other than on batted balls, walks, or hits by pitch.
- R - Run - times reached home base legally and safely
- AVG - Opponents batting average - hits allowed divided by at-bats faced
- BB - Base on balls (also called a "walk") - times pitching four balls, allowing runner to advance to first base
- BS - Blown save - number of times entering the game in a save situation, and being charged the run which ties the game.
- CG - Complete game - number of games where player was the only pitcher for his team
- DIPS - Defense independent pitching statistics - a measure of a pitcher's effectiveness that doesn't include balls in play
- ER - Earned run - number of runs that did not occur as a result of errors or passed balls
- ERA - Earned run average - earned runs times innings in a game (usually nine) divided by innings pitched
- GIR - Games in relief - number of games pitched where player was not the starting pitcher for his team
- GF - Games finished - number of games pitched where player was the final pitcher for his team
- GP - Games pitched - number of games in which the player pitched
- G/F - Ground ball fly ball ratio - ground balls allowed divided by fly balls allowed
- GS - Games started - number of games pitched where player was the first pitcher for his team
- H/9 - Hits per nine innings - hits allowed times nine divided by innings pitched
- HA - Hits Allowed - total hits allowed
- HB - Hit batsman - times hit a batter with pitch, allowing runner to advance to first base
- HLD (or H) - Hold - number of games entered in a save situation, left in save situation, recorded at least one out, and not having surrendered the lead
- HRA - Home runs allowed - total home runs allowed
- IBB - Intentional base on balls
- IRA - Inherited runs allowed - number of runners allowed to score who were on base when pitcher enters the game
- IP - Innings pitched - number of outs recorded while pitching divided by three
- R/9 - Runs per nine innings - number of runs allowed times nine divided by innings pitched
- SHO - Shutout - number of complete games having allowed zero runs
- SO - Strikeout (also abbreviated K) - number of batters who received strike three
- SO/9 - Strikeouts per nine innings - strikeouts times nine divided by innings pitched
- SO/BB - Strikeout-to-walk ratio - number of strikeouts divided by number of base on balls
- SV - Save - number of close games finished where the pitcher's team won
- TBF - Total batters faced - opponent's total plate appearances
- W - Win - number of games where pitcher was pitching while his team took the lead and went on to win (also related: winning percentage)
- L - Loss - number of games where pitcher was pitching while the opposing team took the lead and went on to win
- W+S - Relief wins plus saves - wins plus saves
- WHIP - Walks plus hits per inning pitched - bases on balls plus hits divided by innings pitched
- W/9 - Walks per nine innings - bases on balls times nine divided by innings pitched
- A - Assists - number of outs recorded on a play where a fielder touched the ball, except if such touching is the putout
- CS - Caught stealing - number of times a runner was thrown out by the catcher while attempting to advance on a pitch
- DP - Double plays - one for each double play during which the fielder recorded a putout or an assist.
- E - Errors - number of times a fielder fails to make a play he should have made with common effort, and the offense benefits as a result
- FP - Fielding percentage - total plays (chances minus errors) divided by the number of total chances
- INN - Innings - number of innings that a player is at one certain position
- PB - Passed ball - error charged to the catcher that occurs when the ball is dropped and one or more runners advance
- PO - Putout - number of times the fielder tags, forces, or appeals a runner and he is called out as a result
- RF - Range Factor - ((putouts + assists)*9)/innings played. Used to determine the amount of field that the player can cover
- SB - Stolen bases - number of times a runner advanced on the pitch without being thrown out by the catcher
- TC - Total chances - assists plus putouts plus errors
- TP - Triple play - one for each triple play during which the fielder recorded a putout or an assist
- G - Games played - number of games where the player played, in whole or in part
- WW - "Wasn't Watching" - used by non-official scorekeepers when their attention is distracted from the game - said to have been invented by Phil Rizzuto
- Triple Crown in Major League Baseball
- MLB Most Valuable Player Award winners
- Cy Young Award winners
- MLB Rookie of the Year Award winners
- Gold Glove Award winners
- Official Baseball Rules, Section 10 - Scoring from http://www.mlb.com
- Find statistics for all of major league history at http://www.Baseball-Reference.com/
- The Baseball Cube Statistical Database for Major League, Minor League and College baseball.
- Retrosheet Historical boxscore information
- Baseball Almanac
- The Society for American Baseball Research