n
Sample Size Calculator
How many responses a survey needs for a chosen confidence level and margin of error.
Result…
How it's calculated
n₀ = z² × p(1 − p) ÷ e² (Cochran) n = n₀ ÷ (1 + (n₀ − 1) ÷ N) (finite population)
This is Cochran's formula for estimating a proportion from a simple random sample, with the finite population correction when you enter a population size. Use 50% for the proportion if you have no estimate. It is the number of completed responses, so plan to invite more to allow for non-response.
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