Sample size calculator for proportions
Enter the confidence level, expected proportion and margin of error to get the required sample size.
Result
A 95% confidence level with a 50% proportion and 5% margin of error needs about 385 observations.
Example
Estimate the sample size needed for a proportion at a confidence level and margin of error in your browser. Values stay on your device.
A 95% confidence level with a 50% proportion and 5% margin of error needs about 385 observations.
Processed locally in your browser.
Methodology
n = (z² × p × (1−p)) / e², where z is the z-score for the confidence level, p the expected proportion and e the margin of error.
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