Enter successes and sample size to get a Wilson score interval for a survey percentage. Choose 90%, 95%, or 99%. You can add a finite population size if you sampled a large share of a known group.
The tool is at form.ms/tools/confidence-interval-calculator.
1. Open the calculator
Go to the Confidence Interval Calculator. Successes are the count in the category you care about (yes, satisfied, promoters). Sample size is n.
2. Enter x, n, and a level
Type Successes (x) and Sample size (n). Pick 90%, 95%, or 99%. 95% is the usual default. Leave Population size N blank unless you sampled without replacement from a known finite group.
3. Read the interval
You get the observed percentage plus lower and upper bounds. Wilson stays inside 0 to 100%. This page is for one share, not for NPS (a difference of two percentages).
Nothing is uploaded. For the headline NPS number, use the NPS Calculator.
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