Estimate the proportion with a dichotomous result or finding in a single sample.

This calculator gives both binomial and normal approximation to the proportion.

Instructions: Enter parameters in the red cells. Answers will appear in blue below.

N = Sample size
x = Number in the sample with the result or finding in question
CL = % Confidence level

1. Binomial "exact" calculation:

Proportion of positive results = P = x/N =

Lower bound =

Upper bound =

2. Normal approximation to the binomial calculation:

Standard error of the mean = SEM = √x(N-x)/N3 =

α = (1-CL)/2 =

Standard normal deviate for α = Zα =

Proportion of positive results = P = x/N =

Lower bound = P - (Zα*SEM) =

Upper bound = P + (Zα*SEM) =