Method
p̂ ± z·sqrt(p̂(1−p̂)/n).
Proportion confidence interval
Calculate an approximate normal confidence interval for an observed rate.
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Inputs
Change assumptions
How to use it
Use the result as a transparent planning estimate. Change one assumption at a time, compare scenarios and move to Toolkit when you need system-level simulation.
Limits
For small samples or extreme rates, use a more robust interval such as Wilson.
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Local by design
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