... standard deviation in a player’s batting average (0.039 in Table 1). Thepredicted change in a bat ter’s batting average due to a two s tandard deviation change inthe team’s pitc h ing ER A ... Sean Lahm an , and is a freely available on the intern et for research p ur poses. The data contains exten -sive personal and yearly performance information on players, coach es, and tea ms from1871 ... workers a re significant, and appear to be based on a rationalresponse to the techno logy.3 The Data and BackgroundThe data was obtained from the “Base ball Arch ive” which is copyright ed by Sean...