Sample Size Calculator

Sample Size Calculation for Proportions

Formula

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Large (Infinite) Populations

n = (zs/e)²

where:

z = 
2.576 for 99% level of confidence
1.96 for 95% level of confidence
1.645 for 90% level of confidence

s = p(1-p)    p = estimated proportion

e = desired margin of error

 

Finite Populations

n = (N(zs/e)²)/(N-1+(zs/e)²)

where:

z = 
2.576 for 99% level of confidence
1.96 for 95% level of confidence
1.645 for 90% level of confidence

s = p(1-p)    p = estimated proportion

e = desired margin of error

N = population size