Confidence Interval Calculator
Calculate a z-based confidence interval for a mean using sample mean, sample standard deviation, sample size, and confidence level.
Formula:
CI = mean ± z* · (sd / √n)
Result will appear here.
| Metric | Value |
|---|
Privacy: calculations run locally in your browser. No inputs are stored or transmitted.
How it works
This tool uses common z critical values: 1.645 for 90%, 1.96 for 95%, 2.576 for 99%.
Examples
- mean = 70, sd = 12, n = 100, 95%
- Standard error = sd / √n
- Margin of error = z* × standard error
FAQ
- What does this confidence interval calculator compute?
It computes a z-based confidence interval for a mean using sample mean, sample standard deviation, sample size, and selected confidence level.
- What confidence levels are supported?
This page supports common z-based levels such as 90%, 95%, and 99%.
- Why must sample size be greater than 0?
Because the standard error uses the square root of sample size in the denominator.
- Are calculations stored?
No. Everything runs locally in your browser.