/* chex52.sas                             */
 /* Example 5.2 -- condition of regression */
 /*  problem for changes in X              */
  options ls = 80 ;                        * easier to read output ;
  data a ;
    input x xpe y ynew ;
    cards ;
  1.0  0.999  0.97   1.55
  1.0  1.000  0.98   0.40
  1.1  1.100  1.02   1.55
  1.1  1.101  1.03   0.50
 ;
 run ;
 /* use both y and ynew with original X    */
 /*                                        */
  proc reg data=a ;
    model y ynew = x  ;
    title 'Chex52.sas condition of regression' ;
    title2 'with original X' ;
 run ;
 /* now try them with a change in X        */
 /*                                        */
  proc reg data=a ;
    model y ynew = xpe  ;
    title 'Chex52.sas condition of regression' ;
    title2 'with X+E' ;
 run ;