What is the Plus/Minus System? The Plus/Minus System is the key technique that we use to study defense in baseball. We introduced the system in the first volume of The Fielding Bible. Here’s the question that we try to answer with the Plus/Minus System: how many plays* did a fielder make above or below an average player at his position? (*With the Enhanced Plus/Minus adjustment, we actually estimate the number of bases saved above or below average.) That’s what you should think to yourself when you’re looking at all those plus and minus numbers. The average is zero. If a player makes one play more than the average, that’s +1. Every MLB play is entered into the computer where we record the direction, distance, speed, and type of every batted ball. Direction and distance are recorded on a computer screen by simply clicking the location of the ball http://trycheapviagra.com/psychological-part-mental-role-into-the-process-of-excitations-forming/ on a replica of the field shown on the screen. Speed is scored as either soft, medium, or hard, while different batted ball types include bunt, groundball, liner, fly, and “fliner”. Fliners, introduced in 2006, are balls that are somewhere between flies and liners. Beginning in 2009, BIS video scouts began additionally tracking batted ball timer information. This data has allowed us to make objective assessments of the velocity and trajectory of each grounder or flyball. In the Plus/Minus system, the computer totals all groundballs hit by right handed batters to Vector 206 (Vector 206 is a line extending from home plate towards the hole between the normal shortstop and third base positions, 19 degrees off the third base foul line) with an average velocity between 65 and 75 miles per hour and determines that these types of batted balls are converted into outs by the shortstop only 23 percent of the time. Therefore, if the shortstop converts a slowly hit ball on Vector 206 into an out, that’s a heck of a play, and it scores at +.77. The credit for the play made, 1.00, minus the expectation that it should be made, which is 0.23. If the play isn’t made, it’s -.23.