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Mean Confidence Interval Calculator

Normal-approximation interval for a sample mean.

Tool inputs stay in your browser · optional AI search sends your query

Good to know: Uses mean ± z·s/√n for independent, representative samples with n≥30. It is a normal approximation, not a small-sample t interval or a guarantee about biased samples.

How to use it (step by step)

  1. 1Fill in the boxes: “Sample mean”, “Sample standard deviation”, “Sample size”, “Confidence”. Example numbers are already there so you can see how it works; replace them with yours.
  2. 2The result updates instantly as you type (on a phone it is below the boxes).
  3. 3The bold line is the main answer. Tap Copy next to any value to copy it.

Words to know

Average (mean) / median
Average = add everything and divide by how many. Median = the middle value when sorted; it is not pulled by extreme values.
Standard deviation
How spread out numbers are. Small = numbers are close together; big = they vary a lot.

More in Math

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