Result
Enter values and select Calculate.
Formula and methodology
Known-SD means use z*. Unknown-SD means use Student t* with df = n − 1. Proportions use the Wilson score interval rather than the unstable naive Wald interval.
Worked example
For mean 100, σ = 15, n = 100, and 95% confidence, the interval is approximately 97.0601 to 102.9399.
Assumptions and interpretation
- Inputs and results remain in this browser and are not sent to analytics.
- This tool performs general educational statistical computation; it does not select a study design or validate scientific conclusions.
- Confidence-interval coverage describes repeated use of the method under its assumptions, not a probability assigned to the fixed parameter after calculation.
- Keep full precision for decisions; displayed values are rounded for readability.