95% Confidence interval (CI) for proportion? calculation?

[JoyShan]

I want to calculate 95% CI for proportion/percentage for a dataset as the following. Original dataset a, I would like to have an output dataset b as such. I have tried some program but not sure if it was correct. Do you have different ways to calculate the 95% CI? Thanks for helping in advance. 

Dataset a

Disease   cases   Denominator   proportion
A              2           120                 0.167
B              5           300                 0.167
C              3           1000               0.3
D             11           500                0.2

Dataset B

Disease   cases   Denominator   proportion   CI_low  CI_high
A              2           120                 0.167
B              5           300                 0.167
C              3           1000               0.3
D             11           500                0.2

SAS program I tried: 

data b;
set a;
p=(cases/denominator);
if p=0 then CI_Low=0;
if p=1 then CI_High=1;
if p ne 0 then CI_Low=(1-betainv(.975, (Denominator-cases+1), cases));
if p ne 1 then CI_High=(1-betainv(.025, (Denominator-cases), cases+1);
run;

[Reeza]

Have you looked at PROC FREQ?

[Reeza · Accepted solution]

Here's something to get you started with using PROC FREQ for confidence intervals. Look at the documentation for details on the CI that can be calculated and options available to you. I think some of your percentages are off in your table.

The table created called CI_VALUES holds the confidence intervals, unfortunately not in the format you requested.

*Generate sample data;
data have;
	input disease $ cases denominator;
	cards;
A 2 120
B 5 300
C 3 1000
D 11 500
;
run;

*Expand data to fit within proc freq - may be other ways to do this;
data expand;
	set have;

	do i=1 to cases;
		Value=1;
		output;
	end;

	do i=1 to denominator-cases;
		Value=0;
		output;
	end;
run;

*Sort for output;
proc sort data=expand;
	by disease;
run;

*Generate CIs;ods table binomial = CI_Values;
proc freq data=expand;
	by disease;

	table value/binomial(level='1');
run;