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Sample size

Plan a prevalence survey with transparent assumptions.

Estimate the sample for a single prevalence, using a normal approximation. This is not a power calculation for trials or comparisons.

Your result

Enter your assumptions and run the workshop.

Formula: n₀ = Z²p(1−p)/d². Optional finite-population adjustment: n₀/[1+(n₀−1)/N]. Multiply by the design effect, divide by response proportion and round up once. Review assumptions with a study statistician. WHO STEPS planning reference ↗