Confidence Interval Calculator

Mean confidence interval with margin of error.

Input Parameters

Sample mean

Standard deviation (σ)

Sample size (n)

Confidence level

Confidence interval[94.63231894, 105.3676811]95% (z = 1.96)

Margin of error± 5.367681064

SE2.738612788

175 available

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A confidence interval calculator builds the range mean ± z·σ/√n for 90, 95 or 99% confidence from sample statistics.

What does 95% mean?

About 95 of 100 such intervals from repeated sampling would contain the true mean.

Why does n matter?

The standard error σ/√n shrinks with sample size, so larger samples give narrower intervals.

z or t?

This tool uses z critical values (1.645/1.96/2.576); for tiny samples with estimated σ, t-intervals are slightly wider.