Calculaion of CI intervals by Clopper-Pearson exact method is used

[raja777pharma]

Hi Team,

I am trying to calculate the CI intervals by using the below code, but i am not getting the same results which are generating the CI intervals by other data step code in Computation of CIs for Binomial proportions in SAS and its practical difficulties (lexjansen.com) 

My code is :

ODS OUTPUT Binomial = CI14;
PROC FREQ DATA=firstx;
BY apaneln ;
TABLES avalc/BINOMIAL alpha=0.2 out=n14(rename=(count=nn));
exact binomial;
RUN;
ODS TRACE OFF;

Code from web :

data Test;
 merge ntc_n Nct; 
 by apaneln apanel; 
 prob = count/N; 
 if   prob=0 then CI_LOW=0; 
 if   prob=1 then CI_HIGH=1; 
 if   prob ne 0 then CI_LOW=round((1-betainv(.8,(N-count+1),count)),.0001); 
 if   prob ne 1 then CI_HIGH=round((1-betainv(.2,(N-count),count+1)),.0001); 
    pct_ci = cat (round(prob,0.001),' (', round(CI_LOW,0.001), ', ', round(CI_HIGH,0.001), ')') ;

    proc sort; by apaneln; 
run;

Please let me know how to generate CI values by proc freq as similar above data step

Thank you,

Rajasekhar.

[FreelanceReinh]

Hi @raja777pharma,

Just use the correct beta quantiles: The first argument of your two BETAINV function calls must be 1-a/2 and a/2, respectively, i.e., .9 and .1, not .8 and .2 with alpha=0.2.

[Rick_SAS]

The formula that PROC FREQ uses is given in the documentation section "Binomial Proportions.".

The following DATA step reproduces the output from PROC FREQ by manually coding the formula. 
In the sashelp.class data, there are n=19 observations and n1=9 females.

PROC FREQ DATA=sashelp.class;
   TABLES SEX/BINOMIAL(CL=clopperpearson) alpha=0.2;
   ods select BinomialCLs;
RUN;

data Test;
alpha = 0.2;
n=19;
count=9;
prob = count/n; 
if   prob=0 then CI_LOW=0; 
else do;
   F = quantile("F", alpha/2, 2*count, 2*(n-count+1));
   frac = (n-count+1) / (count*F);
   CI_LOW = 1/(1 + frac);
end;
if prob=1 then CI_HIGH=1; 
else do;
   F = quantile("F", 1-alpha/2, 2*(count+1), 2*(n-count));
   frac = (n-count) / ((count+1)*F);
   CI_HIGH = 1/(1+frac);
end;
keep alpha n count prob CI_LOW CI_HIGH ;
run;
PROC PRINT;RUN;