New baseball statistics seem to be invented every year, measuring another variable in the game and attempting to measure value in a different (sometimes better) way that takes the human element out of the argument.
Many of these stats can be attributed to "sabermetrics," which were born in the 1980s, grew in the 1990s, and really gained traction in the 2000s as many of baseball's front-office decision makers became disciples of some of these statistics as an alternative objective way to evaluate players.
Sabermetrics is derived from the acronym SABR, which stands for the Society for American Baseball Research.
Sabermetrics was coined by renowned baseball author and researcher Bill James. James and others created new statistics with which to measure players' productivity other than the traditional batting averages and ERA. It's often used to measure future productivity.
These are some of the widely used stats derived from sabermetrics, and how to compute them. (If you're new to baseball, you'll need to develop a knowledge of general baseball statistical abbreviations and definitions to understand many of these sabermetrics terms.)
BABIP: Batting average on balls in play. It's the frequency of which a batter reaches a base after putting the ball in the field of play. For pitchers (a measure of the hitters they face), it's a good measure of luck. So pitchers with high or low BABIPs are good bets to see their performances adjust to the mean.
BsR: Base runs. Similar to runs created (see below). It estimates the number of runs a team "should" have scored given their component offensive statistics.
CERA: Component ERA. It's an estimate of a pitcher's ERA based upon the individual components of his statistical line, another statistic that tries to take luck out of the equation.
Def Eff: Defensive efficiency. It's the rate at which balls put into play are converted into outs by a team's defense. Can be approximated with (1 - BABIP).
dERA: This is a measurement of what a pitcher's earned run average would have been, if not for the effects of defense and luck. It uses batters faced, home runs allowed, walks allowed, intentional walks allowed, strikeouts and hit batsmen in a complex mathematical formula.
DICE: Defense-independent component ERA. It's a mathematice formula that measures pitching performance using home runs allowed, walks, hit by pitch, strikeouts and innings pitched.
DIPS: Defense-independent pitching statistics. They are a series of statistics (such as DICE above) that measure a pitcher's effectiveness based only on plays that do not involve fielders: home runs allowed, strikeouts, hit batters, walks, and, more recently, fly ball percentage, ground ball percentage, and line drive percentage.
EqA: Equivalent average. It's a stat used to measure hitters independent of ballpark and league effects. It's a complex formula that takes into account hits, total bases, walks, hit by pitch, stolen bases, sacrifice hits, sacrifice flies, at-bats and caught stealing. It's then normalized for league difficulty.
ERA+: Adjusted ERA. It's earned run average adjusted for the ballpark and the league average.
Fielding Runs Above Replacement: The difference between an average player and a replacement player is determined by the number of plays that position is called on to make.
IR: Inherited runs. It's the number of runners inherited by a relief pitcher that scored while the reliever was in the game.
ISO: Isolated power. It's a measure of a hitter's raw power - extra bases per at-bat.
LIPS: Late-inning pressure situation. It means any at-bat in the seventh inning or later, with the batter's team trailing by three runs or less (or four runs if the bases were loaded).
Runs created: A term to measure how many runs a player creates. Its basic formula is hits plus walks times total bases, divided by at-bats plus walks.
OPS: On-base plus slugging. Measures a batter's ability to get on base and hit for power. It's simply the on-base percentage plus the slugging percentage.
PECOTA: An acronym of Player Empirical Comparison and Optimization Test Algorithm. And it's also an homage to journeyman baseball player Bill Pecota, considered a baseline average player. It's an incredibly complex formula that forecasts a player's performance in all of the major categories used in typical fantasy baseball games, and also forecasts production in advanced sabermetric categories.
PERA: Peripheral ERA. It's a pitching statistic that computes the expected ERA, taking into account park-adjusted hits, walks, strikeouts and home runs allowed.
Pythagorean expectation: It's a formula that resembles the mathematical Pythagorean theorem and is used to estimate how many games a baseball team should have won, based on how many runs a team scored and allowed. Comparing the two percentages can determine how lucky a team was.
QS: Quality start. A game in which a pitcher completes six innings, allowing no more than three runs.
RF: Range factor. Used to determine how much field a player can cover. It's nine times putouts + assists divided by innings played.
TPR: Total player rating. It measures the value of players that allows players to be compared for different positions, teams and eras, used in the Total Baseball encyclopedias.
VORP: Value over replacement player. For hitters, it's the number of runs contributed beyond what a replacement-level player at the same position would contribute.
WAR or WARP: Wins above replacement player. It's a statistic that combines win shares and WORP. It represents the number of wins this player contributed, above what a replacement level hitter, fielder, and pitcher would have done.
WHIP: Walks and hits per inning pitched. It's the average number of walks and hits allowed by the pitcher per inning. (BB + H divided by IP).
Win shares: One of the first sabermetrics statistics, it considers statistics for players in the context of their team, and assigns them a number that's one-third of a team win, using a set of complex mathematics that takes almost 100 pages to explain in Bill James' 2002 book, "Win Shares."
XR: Extrapolated runs, similar to runs created, except it assigns a run value to each event, rather than a multiplicative formula.