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Sample Size Calculator

How many samples for your desired margin of error?

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Margin of Error (±) %Population SD (or 50% for proportions)For proportions use 50 (worst case) Confidence

Results

Required Sample Size —

How to use the Sample Size Calculator

n = (z* × σ ÷ E)². For proportions, σ = 50 gives the safe worst-case size.

Frequently Asked Questions

n=1,067 gives ±3% at 95% confidence for proportions — the industry sweet spot of cost vs precision.

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