data fw04p21; title 'Chapter 4, Exercise 21';
input  OBS    TYPE    TRUE     DIFF ;
cards;
  1      1     1.57    -0.112
  2      1     1.57     0.163
  3      1     1.57    -0.151
  4      1     2.92    -0.117
  5      1     2.95     0.072
  6      1     2.95     0.169
  7      1     4.32    -0.006
  8      1     4.32    -0.092
  9      1     4.32    -0.268
 10      1     5.90     0.119
 11      1     5.90     0.118
 12      1     5.90     0.051
 13      1     7.47    -0.272
 14      1     7.47    -0.302
 15      1     7.47     0.343
 16      2     1.46    -0.094
 17      2     1.57    -0.137
 18      2     1.57     0.308
 19      2     2.95    -0.238
 20      2     2.95     0.031
 21      2     2.95     0.160
 22      2     4.32    -0.385
 23      2     4.32    -0.366
 24      2     4.59    -0.173
 25      2     5.90    -0.259
 26      2     5.90     0.266
 27      2     5.90    -0.303
 28      2     7.47    -0.125
 29      2     7.47     0.383
 30      2     7.47     0.334
 31      3     1.57     0.060
 32      3     1.57     0.106
 33      3     1.57     0.084
 34      3     2.95    -0.016
 35      3     2.95    -0.191
 36      3     2.95     0.097
 37      3     4.32    -0.024
 38      3     4.32    -0.046
 39      3     4.32    -0.178
 40      3     5.90     0.040
 41      3     5.90     0.028
 42      3     5.90     0.619
 43      3     7.47     0.062
 44      3     7.47     0.293
 45      3     7.50    -0.106
 46      4     1.46    -0.034
 47      4     1.57     0.116
 48      4     1.57     0.055
 49      4     2.92    -0.023
 50      4     2.95    -0.099
 51      4     2.95    -0.212
 52      4     4.32    -0.256
 53      4     4.32    -0.110
 54      4     4.32    -0.272
 55      4     5.90    -0.046
 56      4     5.90     0.009
 57      4     5.90    -0.134
 58      4     7.47    -0.050
 59      4     7.47     0.009
 60      4     7.50    -0.034