Calculateur de Confidence Interval
Calculate a confidence interval for a sample mean given standard deviation and sample size.
Formula and method
This calculator computes Margin of error, Lower bound, Upper bound directly in your browser without sending data to an external server.
Mathematical formula
- Margin of error:
z × (stdDev ÷ √(n)) - Lower bound:
mean - z × (stdDev ÷ √(n)) - Upper bound:
mean + z × (stdDev ÷ √(n))
Variables and parameters
- Sample mean (mean): default value 100.
- Standard deviation (stdDev): default value 15.
- Sample size (n): default value 30.
- Z-score (95% = 1.96) (z): default value 1.96.
Some formulas are undefined for certain input combinations (such as division by zero or logarithms of non-positive numbers). In those cases the live tool displays an alert instead of NaN.
Embed this tool
Paste this snippet into your own site or blog post to embed a live, working copy of this tool. It links back to the full page on SpecWhale.
Frequently asked questions
What equation and variables does Confidence Interval Calculator use?
Confidence Interval Calculator evaluates outputs such as <strong>Margin of error, Lower bound, Upper bound</strong> based on inputs including Sample mean, Standard deviation, Sample size, Z-score (95% = 1.96). Check the Mathematical Method section for the explicit formula.
What happens if I enter invalid or zero values into Confidence Interval Calculator?
If an input combination is mathematically undefined (such as division by zero or negative square roots), SpecWhale alerts you gracefully rather than returning invalid NaN outputs.
Are my calculations in Confidence Interval Calculator saved or private?
All calculations are 100% private and run locally in your Web browser. Your numbers are never uploaded to any server, but can be saved locally to your device or exported as CSV/JSON.
Is Confidence Interval Calculator free to use?
Yes. Confidence Interval Calculator is completely free, has no usage limit, and does not require an account, email, or API key.
Does Confidence Interval Calculator store or upload my data?
No. Confidence Interval Calculator calculates everything locally in your browser. Nothing you type is sent to a server or stored by SpecWhale.
How accurate is Confidence Interval Calculator?
Confidence Interval Calculator uses a standard formula (see the Method section above for the exact expression). For high-stakes financial, medical, or legal decisions, confirm the result with a professional or an authoritative source before relying on it.
Can I embed Confidence Interval Calculator on my own website?
Yes. Use the "Embed this tool" snippet on this page to add a free, working copy of Confidence Interval Calculator to your own blog post or page.