Proportion Confidence Interval Calculator
Calculate a bounded Wilson score interval from a success count and sample size.
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How to use Proportion Confidence Interval Calculator
Wilson score uses denominator 1+z²/n, center (p+z²/(2n))/denominator, and half-width z×sqrt(p(1−p)/n+z²/(4n²))/denominator.
- Enter observed successes, sample size, confidence fraction (0.5–0.999).
- Check the model, units, and supported limits before calculating.
- Run the tool, inspect the result, then copy or download it.
Good to know
- Whole successes 0≤x≤n, n≥1. Independent binomial observations; no survey weights, clustering, continuity correction, or exact Clopper–Pearson claim.
- Runs locally. Numeric inputs are bounded; floating-point output is approximate and rounded to 12 significant digits. Unsupported or non-finite calculations produce an error.
Common questions
How does Proportion Confidence Interval Calculator calculate its result?
Wilson score uses denominator 1+z²/n, center (p+z²/(2n))/denominator, and half-width z×sqrt(p(1−p)/n+z²/(4n²))/denominator.
What assumptions and boundaries apply?
Whole successes 0≤x≤n, n≥1. Independent binomial observations; no survey weights, clustering, continuity correction, or exact Clopper–Pearson claim.
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