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 green cells. Answers will appear in the blue box 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 = Z_α =

Proportion of positive results = P = x/N =

Lower bound = P - (Z_α*SEM) =

Upper bound = P + (Z_α*SEM) =