Wilson Proportion Interval Calculator
Estimate a binomial proportion and an approximate 95% Wilson score interval, including zero-event samples.
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Estimate a binomial proportion with an approximate 95% Wilson score interval. All default values are fictional.
Calculation results
Observed proportion: 0.25
95% lower limit: 0.111862
95% upper limit: 0.468701
Assumptions and limits
Independent Bernoulli observations with one common probability. Unadjusted two-sided Wilson interval without continuity correction; not exact coverage. Allows zero or all events. Not for clustered, weighted, paired or censored observations. Counts must be whole numbers, total 1–100 million.
NIST: confidence limits for a proportion · Read the practical guide · Download blank worksheet (TXT)