Speed Score is a statistic

Statistic

A statistic is a single measure of some attribute of a sample . It is calculated by applying a function to the values of the items comprising the sample which are known together as a set of data.More formally, statistical theory defines a statistic as a function of a sample where the function...

 used in Sabermetric studies to evaluate a baseball

Baseball

Baseball is a bat-and-ball sport played between two teams of nine players each. The aim is to score runs by hitting a thrown ball with a bat and touching a series of four bases arranged at the corners of a ninety-foot diamond...

 player's speed. It was invented by Bill James

Bill James

George William “Bill” James is a baseball writer, historian, and statistician whose work has been widely influential. Since 1977, James has written more than two dozen books devoted to baseball history and statistics...

, and first appeared in the 1987 edition of the Bill James Baseball Abstract.http://members.cox.net/sroneysabr/JamesIndex/Abstract1987.html

Speed Score includes five factors: stolen base percentage, stolen base attempts as a percentage of opportunities, triples, double plays grounded into as a percentage of opportunities, and runs scored as a percentage of times on base.http://www.baseballprospectus.com/glossary/index.php?mode=viewstat&stat=165 Baseball Prospectus

Baseball Prospectus

Baseball Prospectus is an organization that publishes a website, BaseballProspectus.com, devoted to the sabermetric analysis of baseball. BP has a staff of regular columnists and provides advanced statistics as well player and team performance projections on the site...

has developed a modified version of Speed Score that equally weights each component.http://www.baseballprospectus.com/glossary/index.php?mode=viewstat&stat=165