Find the confidence intervals for proportions

sas_proportion_confidence_intervals.sas

/*This program calculates binomial percentages and confidence limits.
Howver, this has no correction methodology so the lower bound can go below 0.
In this case a different method is needed*/


*set table name to summarize;
%let dsin=sashelp.class;
*set variable name to get percentages;
%let var = sex;
*set name of output data set;
%let dsout = Want;


*get counts of each by group and the total count;
proc sql noprint;
create table _freq as
select &var., count(*) as N
from &dsin
group by &var.;
select count(*) into :Ntotal from &dsin.;
quit;

*calculate percentages and upper/lower confidence limits;
data &dsout.;
set _freq;

Ntotal=&ntotal.;
PCT = n/Ntotal;

STD = ((PCT*(1-PCT))/NTotal)**(1/2);

UL = PCT + 1.96*STD;
LL = PCT - 1.96*STD;

run;

*remove temporary tables;
proc sql noprint;
drop table _freq;
quit;