Confidence Level Calculator
Convert a z critical value into a two-sided confidence level, central area, and tail probabilities under the standard normal distribution.
Two-sided confidence level:
CL = 2Φ(z) − 1
| Metric | Value |
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Privacy: calculations run locally in your browser. No inputs are stored or transmitted.
How it works
This tool uses the standard normal CDF to convert a z critical value into:
central confidence level, left-tail area, and right-tail area.
Examples
- z = 1.645 → about 90% confidence
- z = 1.96 → about 95% confidence
- z = 2.576 → about 99% confidence
FAQ
- What does this confidence level calculator compute?
It converts a z critical value into the corresponding two-sided confidence level and tail areas under the standard normal distribution.
- What is a z critical value?
It is the cutoff value on the standard normal distribution used for constructing confidence intervals.
- Is this for two-sided confidence intervals?
Yes. This calculator interprets the input z value as a symmetric two-sided confidence interval cutoff.
- Are calculations stored?
No. Everything runs locally in your browser.