Data for some baseball players in 1970, from Efron and Morris (1975)
and The Baseball Encyclopedia.  Table 6.1 of Bayesian Data Analysis

player y.bar post.median previous.avg previous.atbats avg.1970
A  .267  .264  .118    51  .224 
B  .156  .239  .249  3514  .183 
C  .311  .273  .246  2244  .276 
D  .200  .249  .264  3210  .279 
E  .400  .290  .314  8142  .352 
F  .356  .281  .275  4826  .283 
G  .333  .277  .255  1139  .238 
H  .289  .268  .248  2753  .266 
I  .178  .243  .256    86  .302 
J  .222  .255  .255  2281  .261 
K  .378  .286  .303  7542  .306 
L  .222  .255  .234   291  .225 
M  .244  .259  .281  5658  .267 
N  .222  .254  .250  2065  .296 
O  .311  .273  .244   454  .274 
P  .244  .259  .244  1967  .233 
Q  .222  .255  .257  1216  .258 
R  .222  .254  .271   888  .251