Confidence interval calculator
Calculate a Wilson score confidence interval for a survey proportion from successes, sample size and confidence level. The calculation runs in your browser; your inputs stay on this device.
Confidence interval for a proportion
Wilson score interval for one survey proportion, generally better behaved than a basic normal interval near 0% or 100%.
Formula and assumptions
Wilson score interval for a binomial proportion using the selected normal critical value; this is not the basic Wald interval.
These estimates assume independent observations and simple random samples where applicable. They do not adjust for complex designs, weighting, clustering or multiple comparisons. Read the result with the underlying study design in mind.
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Frequently asked questions
Are my inputs sent to PulseLake?
No. The calculation runs in your browser; the form does not submit the values, and these calculators do not use a server-side analysis service.
Do these results handle weighting or complex survey samples?
No. The methods assume independent simple random observations and do not account for weighting, clustering, repeated measures or nonresponse.
Does statistical significance establish practical importance?
No. Review the interval and whether effects of that size matter for the decision. A non-significant result does not prove groups are identical.
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