Sample Size for a Proportion

5%
50%

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Formula

Sample Size for a Proportion

n=Z2×p×(1−p)d2×(N−1)+Z2×p(1−p)n = \frac{Z^2 \times p \times (1 - p)}{d^2 \times (N - 1) + Z^2 \times p(1 - p)}

Where:

  • n = required sample size
  • N = population size
  • Z = Z-score (e.g., 1.96 for 95% confidence)
  • p = estimated proportion
  • d = margin of error