* Use Durbin-Watson Statistic to test if
  residuals are uncorrelated;

options linesize=70 nodate pagenum=1;
data salesdw;
   infile "c:/datasets/sales.txt" firstobs=2;
   input t sales;
   label t="Month Number"
         sales="Monthly Sales";

proc reg;
   title "SalesDW Example";
   model sales = t / dw;
   plot r.*p. r.*nqq.;

proc autoreg;
   model sales = t / nlag=1;

run;
quit;