Confidence Interval Calculator

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Build a confidence interval for a mean from the sample mean, standard deviation and size. See the margin of error, lower and upper bounds and the z critical value. Free and live.

%
Confidence interval –
Margin of error –
Lower bound –
Upper bound –
Z critical value –
Uses the z distribution, which assumes a large sample (n ≥ 30) or a known population standard deviation. The interval is mean ± z · σ ⁄ √n. For small samples, a t distribution is more appropriate.
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