data lln;
call streaminit(7777);
do i=5 to 500;
 x=rand('bern',0.2);
 output;
end;
run;
data lln;
 set lln;
 sum+x;
 phat=sum/_n_;
run;

proc sgplot data=lln;
series x=i y=phat;
refline 0.2/axis=y;
run;