User:Alexdasilva47/On-base percentage

Statistical Variations

Due to the improved statistical analysis of baseball, many variations of OBP have been created. Some of the more common variations include On-base Plus Slugging (OPS), On-base Plus Slugging Plus (OPS+) and Weighted On-base Average (wOBA). Each are formulated as follows:

$$OPS = OBP + SLG$$

where

SLG = Slugging Percent

Used as an overall measure of a player's offensive output, OPS simply combines OBP and SLG, measures of how often a player gets on base and the average number of bases per at-bat, respectively. It's use, although relatively common, is treated with scrutiny due to its treatment of OBP and SLG as of equal importance, yet it has been determined that OBP is almost twice as valuable as SLG.

$$OPS+ = (\frac{100}{BPF}) * (\frac{OBP}{lgOBP} + \frac{SLG}{lgSLG} -1 )$$

where

BPF = Batting Park Factor

lgOBP = League Average OBP

lgSLG = League Average SLG

Similar to OPS, OPS+ accounts for the additional factor of which ballpark is in use. Furthermore, OPS+ is scaled to be more easily understood, with 100 being league average, and each point above/below is one percent above/below league average; i.e. a OPS+ of 95 is 5% below league average.

$$wOBA = \frac{wBB*BB + wHBP*HBP + w1B*1B + w2B*2B + w3B*3B + wHR*HR}{AB + BB - IBB + SF + HBP}$$

where

wBB = Weight of Bases on Balls

wHBP = Weight of Hit By Pitch

w1B = Weight of Single

w2B = Weight of Double

w3B = Weight of Triple

wHR = Weight of Home Run

IBB = Intentional Bases on Balls

A more advanced statistic, wOBA was created by statistical analyst Tom Tango to measure a batter's overall offensive production through one number. The main premise behind wOBA is that not all ways on base are created equal, that is, a home run is worth more than a walk, and a double more than a single. The use of traditional stats, such as batting average (BA) and OBP puts equal emphasis on each hit and way on base. wOBA uses linear weights to value each plate appearance outcome. Each season, the weights change based on the value of each using a run expectancy matrix. In simple terms, each base-out scenario (i.e. one out, runner on second or two outs, runners on first and third) is collected and the average number of runs produced by each plate appearance outcome is produced. This average then becomes the linear weights used in the calculations of wOBA.