User:Jprg1966/Glossary of sabermetrics

Sabermetrics is the application of statistical analysis to baseball. Sabermetrics was developed by baseball statisticians beginning in the 1980s when they judged traditional baseball statistics to lack precision and accuracy. Its leading pioneer was Bill James.

A

adjusted ERA+ (ERA+)

ERA+ compares a pitcher's ERA to the league average ERA and controlling for park factors. Average ERA+ is 100, with any score above that indicating better-than-average performance. ERA+ allows for easier comparisons of pitchers across periods of history.

B

base runs (BsR)

Similar to runs created, BsR is an attempt to quantify the number of runs a team or pitcher "should" score or allow given certain statistics. It attempts to measure the interaction effects of offensive events, as opposed to tabulating their raw value.

batting average on balls in play (BABIP)

BABIP measures the percentage of balls struck in fair territory that result in base hits. It is often used in comparison to a batting average or batting average against in order to determine whether a hitter or pitcher has had his average affected by "fluke" events. Over time, BABIP tends to regress toward about .300.

C

component ERA (ERC)

ERC is a formula used to forecast a pitcher's ERA based on his hits and walks allowed.

D

Defense independent pitching statistics (DIPS)

DIPS is a group of statistics that attempt to isolate the effect of a pitcher's team's defense on his pitching performance.

Defense-Independent ERA (dERA)

dERA is an estimate of a pitcher's ERA absent the effects of his team's defense.

Defense-Independent Component ERA (DICE)

DICE is a variant of the component ERA aiming to correct for the effects of the pitcher's team's defense.

E

equivalent average (EQA)

EQA represents a player's batting average absent park and league factors.

F

fielding independent pitching (FIP)

FIP is a metric, scaled to resemble an ERA, that focuses on events within the pitcher's control — home runs, walks, and strikeouts. A variant, known as xFIP, substitutes a pitcher's own home run percentage with the league

I

isolated power (ISO)

ISO measures a hitter's ability to hit for extra bases by subtracting batting average from slugging percentage.

L

left on base percentage (LOB%)

LOB% represents the percentage of baserunners a pitcher does not allow to score. LOB% tends to regress toward 70–72% over time, so unusually high or low percentages could indicate that pitcher's ERA could be expected to rise or lower in the future. An occasional exception to this logic is a pitcher with a very high strikeout rate.

U

ultimate base running (UBR)

UBR assigns linear weights to every individual baserunning event in order to measure the impact of a player's baserunning skill.

ultimate zone rating (UZR)

UZR measures the ability of a player to defend an assigned "zone" of the field compared to an average defensive player at his position.

V

value over replacement player (VORP)

VORP is a statistic that calculates a player's overall value in comparison to a "replacement-level" player. There are separate formulas for players and pitchers.

W

walks plus hits per inning pitched (WHIP)

WHIP calculates the number of baserunners a pitcher allows per inning. It has become a fairly mainstream statistic, being featured prominently on the player pages of sites like ESPN.com and Yahoo! Sports.

weighted runs created (wRC)

An updated version of runs created (RC), this statistic measures in runs the overall offensive impact of a player. It is based on the formula used in wOBA (see below). wRC+, similar to OPS+, is scaled so that the league average is 100 after adjusting for park and league effects.

whiff rate

Whiff rate is a term, usually used in reference to pitchers, that divides the number of pitches swung at and missed by the total number of swings in a given sample. If a pitcher throws 100 pitches at which batters swing, and the batters fail to make contact on 26 of them, the pitcher's whiff rate is 26%.

win shares

Win shares is a complex metric that gauges a player's overall contribution to his team's wins.

weighted on-base average (wOBA)

wOBA is a formula to determine a hitter's average offensive contribution per plate appearance. It is weighted to produce a number similar to a standard on-base percentage.

wins above replacement (WAR)

WAR represents the number of wins a player contributes to his team over a "replacement-level player." There is no standard formula for this statistic, with several websites offering their own formulas.