data sales;
infile "c:/csc423/week7/sales.txt";
input PROFIT AREA POPN OUTLETS COMMIS;
profout=profit/outlets;
comout=commis*outlets;

proc corr;
var profit area popn outlets commis;
run;

proc reg;
model profit=area popn commis outlets;
plot student.*predicted.;
plot npp.*student.;
plot student.*area;
output student=resid;
run;
proc univariate;
var resid;
probplot/normal(mu=est sigma=est);
run; quit;