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Cold email confidence interval calculator
Calculate a 95% Wilson score interval around a binary outcome rate, including zero-outcome samples.
Prepare your inputs
Define one outcome per independent observation. A unique person either meets the chosen reply criterion by the cutoff or does not. Do not enter total reply messages against a denominator of unique people.
Runs in this browser. Inputs are not sent by this tool or saved in browser storage. Start with the fictional example; use redacted text for reviews.
How it works
The Wilson score method keeps bounds within zero and one and remains informative when observed outcomes are zero or all observations succeed. The output displays the observed rate and both bounds.
Worked example
For 10 outcomes among 100 observations, the observed rate is 10%. The Wilson interval is approximately 5.52%–17.44%, showing uncertainty that a bare percentage hides.
Limits and interpretation
The model does not repair selection bias or dependence among observations. A confidence interval is not a guarantee for a future campaign and is not an A/B winner test.
Examples are synthetic, not customer results. NIST: confidence intervals for a proportion