/*
Does exact 2-sided test of binomial parameter

INPUT:
-> n,  sample size
-> y,  observed number of "successes"
-> p0, value of parameter p under H0

OUTPUT: p-values:
p_plus:       versus Ha:p>p0
p_minus:      versus Ha:P<p0
p_plus_minus: versus Ha: p >< p0
*/
%macro binexact(n,y,p0);
data binexact;
pval_plus=0;
pval_minus=0;
pval_plus_minus=0;
do i=0 to &n;
 pval_plus=pval_plus+PDF('BINOMIAL',i,&p0,&n)*(i>=&y);
 pval_minus=pval_minus+PDF('BINOMIAL',i,&p0,&n)*(i<=&y);
 pval_plus_minus=pval_plus_minus+PDF('BINOMIAL',i,&p0,&n)*(PDF('BINOMIAL',i,&p0,&n)<=PDF('BINOMIAL',&y,&p0,&n));
end;
drop i;
run;
proc print;run;
%mend binexact;
/*
Sample calls from lecture notes:
%binexact(6,3,.667);
%binexact(10,9,.5);
*/