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In baseball, Defense Independent Pitching Statistics (DIPS) are statistics which measure a pitcher's effectiveness based only on plays which do not involve fielders: home runs allowed, strikeouts, hit batters and walks. Those plays are under only the pitcher's control in the sense that fielders have no effect on their outcome.

There are several sabermetric statistics that use only these "defense-independent" pitching statistics to evaluate a pitcher's ability. The logic behind using only these statistics is based on research suggesting that there is little to no difference in the abilities of Major League pitchers to influence the rate of hits against them on balls hit into the field of play. In other words, defense-independent statistics such as walks and strikeouts are determined almost entirely by the pitcher's ability level. But defense-dependent statistics, such as the rate of hits allowed on balls put into play (other than home runs), are almost entirely the result of luck and the skills of the defensive players on the field.

Voros McCracken's research was the earliest to detail and publicize these effects. Until his article in 2001, much of the baseball research community believed that individual pitchers had an inherent ability to prevent hits on balls in play. McCracken reasoned that if this ability existed, it would be noticeable in a pitcher's 'Batting Average on Balls In Play' (BABIP). His research found the opposite to be true: that while a pitcher's ability to cause strikeouts or allow home runs remained somewhat constant from season to season, his ability to prevent hits of balls in play did not.

However another study, by Tom Tippett at Diamond Mind, while confirming many of McCracken's findings, concluded that the differences between pitchers in preventing hits on balls in play were at least partially the result of skill.]. Tippett analyzed certain groups of pitchers that appear to be able to reduce the number of hits allowed on balls hit into the field of play (BHFP). Like McCracken, Tippett found that a pitcher's BABIP was very volatile on an annual basis. It varied much more widely each year from a pitcher's career average than did home runs or walks. But he also found large and significant differences between pitchers' career averages. In many cases, it was these differences that accounted for the pitchers' relative success.

To better evaluate pitchers in light of his theory, McCracken developed "Defense-Independent ERA" (dERA), the most well-known defense-independent pitching statistic. McCracken's formula for dERA is incredibly complicated, with a number of steps. A simpler formula, known as Defense-Independent Component ERA (DICE) was created by Clay Dreslough in 2001 and can be calculated using simple math:

${\displaystyle DICE=3.00+{\frac {13HR+3(BB+HBP)-2K}{IP}}}$

In that equation, "HR" is home runs, "BB" is walks, "HBP" is hit batters, "K" is strikeouts, and "IP" is innings pitched. That equation gives a number that is better at predicting a pitcher's ERA in the following year, when compared to the pitcher's actual ERA in the current year.

Neither DIPS ERA (dERA) nor DICE are as useful for knuckleballers and other "trick" pitchers. Recent research indicates that pitchers with extremely slow changeups are systematically underrated by dERA, although the validity of this research has been questioned by some.

However, in recent years, McCracken has created version 2.0 of dERA, which incorporates the value of knuckleballers and other types of pitchers in affecting the number of hits allowed on balls hit in the field of play (BHFP).

Despite Tippetts's claims, the work done by McCracken and others on DIPS is regarded by many in the sabermetric community as the most important piece of baseball research done in many years. They believe McCracken's work still appears to show that this effect is smaller than the conventional wisdom had assumed.

Alternate Formulae

FIP

Tom Tango, an internet sabermetrician, publicized a simpler formula, known as Fielding Independent Pitching, which is very close to the results of dERA and DICE.

${\displaystyle FIP={\frac {13HR+3BB-2K}{IP}}}$

In that equation, "HR" is home runs, "BB" is walks, "K" is strikeouts, and "IP" is innings pitched. That equation gives you a number that is nothing close to a normal ERA, so the equation used is more often (but not always) this one:

${\displaystyle FIP={\frac {13HR+3BB-2K}{IP}}+3.20}$

That equation gives a number that is much closer to a potential pitcher's ERA.

The Hardball Times, a popular baseball statistics website, uses a slightly different FIP equation, instead using 3*(BB+HBP) rather than simply 3*(BB) where "HBP" stands for batters hit by pitch.

See also

• Baseball statistics
• Sabermetrics

External links

• Larry Mahnken's DIPS Worksheets
• The Hardball Times' Statistical Glossary
• Tom Tango's Tangotiger Site, introducing FIP
• DICE explanation page at sportsmogul.com
• Pitching and Defense: How Much Control Do Hurlers Have? by Voros McCracken
• Jay Jaffe's summary and updating of DIPS statistics, 2004

• Baseball statistics