options nocenter;

data problem81;
 infile 'i:\.www\datasets502\EX0502.DAT' firstobs=2 dlm='09'x;
 input person sbp quet age smk;

/* Investigate different models */
proc reg;
 model sbp = quet;
 model sbp = quet age;
 model sbp = quet age smk /ss1;
run;