/* chex98.sas                                            */
 /*   Example 9.8 -- Finney logistic regression problem   */
 /*   y = number of positive responses (constriction)     */
 /*   x1 = air flow rate                                  */
 /*   x2 = volume                                         */
 /*                                                       */
  options ls=80 ;
  data a ;
    infile '~/www/aug00/chap9/finney.dat' ;
    input x1 x2 y ;
    lx1 = log(x1) ;
    lx2 = log(x2) ;
 ;
 run ;
 /*                                                       */
 /*                       write out the data              */
  proc print data=a ;
    title 'Example 9.8 -- Finney logistic regression problem' ;
 run ;
 /*                                                       */
 /*                       logistic regression             */
 /*               (1-y) is Bernoulli(p), so Pr(Y=0) = p   */
 /*                   logit(p) = b0 + b1*lx1 + b2*lx2     */
  proc logistic data=a ;
    model y = lx1 lx2 ;
 run ;