Confidence Interval Calculator (Proportion)
Wald normal-approximation CI for a proportion — 90/95/99% two-sided intervals with standard error and adequacy check.
Also available in 한국어
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95% confidence interval
[78.00%, 92.00%]
- Sample proportion
- 85.00%
- Margin of error (±)
- 7.00%
How it was calculated
- 85.00%01Sample proportion
p̂ = 85 / 100
Basis: Point estimate of the population proportion
- 3.57%02Standard error
SE = √(p̂(1−p̂)/n) = √(0.85000 × 0.15000 / 100)
Basis: Standard error of the proportion estimator
- 7.00%03Confidence interval (95%)
0.85000 ± 1.96 × 0.03571 = [0.78001, 0.91999]
Basis: Wald normal approximation — z(95%) = 1.96 (two-sided)
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