Confidence Interval Calculator

This calculator creates a confidence interval for a population mean using the following formula:

Confidence Interval = x +/- z*(s/√n)

where:

  • x: sample mean
  • z: z-value that corresponds to confidence level
  • s: sample standard deviation
  • n: sample size

To create a confidence interval for a population mean, simply fill in the values below and then click the “Calculate” button:

90% Confidence Interval: (5.896, 28.104)

95% Confidence Interval: (3.770, 30.230)

99% Confidence Interval: (-0.388, 34.388)

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2 Replies to “Confidence Interval Calculator”

  1. This site looks great – thanks for all the hard work!

    If I wanted to use this to find the confidence interval for an intervention, would I be using a value of n which looks at the entire sample (ie control and treatment branches) or just the treatment one?

    Sorry for the noob question!

  2. This calculator is not correct — it is using the “sample” std deviation as the **population** std deviation.

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