 
C_{L} = 
a − b 
C_{U} = 
a + b 


c 
c 
where:
 C_{L} and C_{U} are the lower and upper confidence limits,
 a = p +(z^{2}/2n) ,
b = 
z 
√
 
pq + (z^{2}/4n) 

n 
 c = 1+ z^{2}/n,
 p and q are the proportions in the sample with and without the character of interest,
 n is the sample size,
 z is the 1 − α/2 percentile of the standard normal distribution where α is the significance level; for a 95% confidence interval z = 1.96.

