Mean Confidence Interval — Known SD

How to use Mean Confidence Interval — Known SD

The known-sigma normal interval is sample mean ± z(1−alpha/2)×population SD/sqrt(n). Confidence describes repeated-sample coverage under the model.

1. Enter sample mean, known population standard deviation, sample size n, confidence fraction (0.5–0.999).
2. Check the model, units, and supported limits before calculating.
3. Run the tool, inspect the result, then copy or download it.

Good to know

• Population SD must be known, positive, and independent of the sample estimate. Normal population or an adequate sampling approximation is required. No Student-t/sample-SD mode is provided.
• Runs locally. Numeric inputs are bounded; floating-point output is approximate and rounded to 12 significant digits. Unsupported or non-finite calculations produce an error.