options linesize=72 nodate nonumber;
data diet;
input level n av_food;
datalines;
0.25	4	10.075
0.65	5	11.64
1.30	5	11.10
1.71	4	11.85
;
proc print;
proc reg;
model av_food = level;
weight n;
run;
proc plot;
plot av_food*level;
run;