Sample Size Calculator to Estimate Population Proportion

Online sample size calculator to estimate population proportion (prevalence) with a specified level of precision. The estimation of the desired precision can also be called as the acceptable error in the estimation which is half the width of the desired confidence interval. This sample size calculator estimates the true value with the desired precision and confidence based on the both infinite population and for a population of the specified size.

Sample Size to Estimate a Proportion with Specified Precision

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Online sample size calculator to estimate population proportion (prevalence) with a specified level of precision. The estimation of the desired precision can also be called as the acceptable error in the estimation which is half the width of the desired confidence interval. This sample size calculator estimates the true value with the desired precision and confidence based on the both infinite population and for a population of the specified size.

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Formula:

Population Sample Size (n) = (Z2 x P(1 - P)) / e2 Where, Z = Z Score of Confidence Level P = Expected Proportion e = Desired Precision N = Population Size For small populations n can be adjusted so that n(adj) = (Nxn)/(N+n)

Example:

Calculate population sample size to estimate a proportion of about 30%, confidence level of 95%, desired precision of 5% and population size of 1000.

Solution:

Population Sample Size (n) = (Z2 x P(1 - P)) / e2
= (0.952 x 0.3(1 - 0.3)) / 0.052
= 245

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