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Example 55.1: Aerobic Fitness Prediction

   *-------------------Data on Physical Fitness-------------------*
   | These measurements were made on men involved in a physical   |
   | fitness course at N.C.State Univ. The variables are Age      |
   | (years), Weight (kg), Oxygen intake rate (ml per kg body     |
   | weight per minute), time to run 1.5 miles (minutes), heart   |
   | rate while resting, heart rate while running (same time      |
   | Oxygen rate measured), and maximum heart rate recorded while |
   | running.                                                     |
   | ***Certain values of MaxPulse were changed for this analysis.|
   *--------------------------------------------------------------*;
   data fitness;
      input Age Weight Oxygen RunTime RestPulse RunPulse MaxPulse @@;
      datalines;
   44 89.47 44.609 11.37 62 178 182   40 75.07 45.313 10.07 62 185 185
   44 85.84 54.297  8.65 45 156 168   42 68.15 59.571  8.17 40 166 172
   38 89.02 49.874  9.22 55 178 180   47 77.45 44.811 11.63 58 176 176
   40 75.98 45.681 11.95 70 176 180   43 81.19 49.091 10.85 64 162 170
   44 81.42 39.442 13.08 63 174 176   38 81.87 60.055  8.63 48 170 186
   44 73.03 50.541 10.13 45 168 168   45 87.66 37.388 14.03 56 186 192
   45 66.45 44.754 11.12 51 176 176   47 79.15 47.273 10.60 47 162 164
   54 83.12 51.855 10.33 50 166 170   49 81.42 49.156  8.95 44 180 185
   51 69.63 40.836 10.95 57 168 172   51 77.91 46.672 10.00 48 162 168
   48 91.63 46.774 10.25 48 162 164   49 73.37 50.388 10.08 67 168 168
   57 73.37 39.407 12.63 58 174 176   54 79.38 46.080 11.17 62 156 165
   52 76.32 45.441  9.63 48 164 166   50 70.87 54.625  8.92 48 146 155
   51 67.25 45.118 11.08 48 172 172   54 91.63 39.203 12.88 44 168 172
   51 73.71 45.790 10.47 59 186 188   57 59.08 50.545  9.93 49 148 155
   49 76.32 48.673  9.40 56 186 188   48 61.24 47.920 11.50 52 170 176
   52 82.78 47.467 10.50 53 170 172
   ;
   proc reg data=fitness;
      model Oxygen=Age Weight RunTime RunPulse RestPulse MaxPulse
            / selection=forward;
      model Oxygen=Age Weight RunTime RunPulse RestPulse MaxPulse
            / selection=backward;
      model Oxygen=Age Weight RunTime RunPulse RestPulse MaxPulse
            / selection=maxr;
   run;

The FORWARD model-selection method begins with no variables in the model and adds RunTime, then Age,...