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Sample size for a Confidence interval of a difference between means

Confidence interval
Confidence Interval (%): 
Input
Pooled standard deviation: 
Confidence interval width (2-sided): 
Ratio of sample sizes in Group 1 / Group 2: 
Results
Number of cases required in group 1:
Number of cases required in group 2:
Total sample size (2 groups together):

For details, see the MedCalc manual: Confidence interval sample size: Difference between means.

How to cite this page

  • MedCalc Software Ltd. Sample size calculator for a Confidence interval of a difference between means | MedCalc. https://www.medcalc.org/en/calc/sample-size-ci-difference-between-means.php (Version 23.6.1; accessed July 15, 2026)
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