In this excerpt, Eddie and Rob refer extensively to SD scores. Using the example given in the Introduction, if group A is 1,2,3,4,5 and group be is 1,3,3,4,4, then both groups have an average, or mean, of 3.0, but group A has an SD of 1.4 whereas group B has an SD of 1.1. The concept of SD is important when making historical comparisons in baseball because, through time, the SD of performance for players and teams has tended to get smaller. An SD score of 0.00 would represent an average team. Negative SD scores represent below-average teams.
T alk about trying to hit a moving target.
Major league baseball changed dramatically for much of the late nineteenth century. In 1892, there was one. In 1881, a walk took seven balls. In 1884, the National League dropped it to six, but returned to seven in 1886 while the American Association dropped to six the same year. Starting in 1885, the National League allowed one side of the bat to be flat, but not the American Association.