Sample size to detect a significant difference between 2 means with equal sample sizes and variances

Input Values


This utility calculates the sample size required to detect a statistically significant difference between two sample means with specified levels of confidence and power, assuming equal sample sizes and equal variances.

Inputs are the assumed true values for the two means, the desired level of confidence and the desired power for the detection of a significant difference and the estimated combined variance. By default, calculations assume that a two-tailed statistical test will be used, but a one-tailed test can also be specified if preferred.

The program outputs the sample size required to detect the specified difference with desired power and confidence, for a one-tailed or two-tailed statistical test, as specified.

Mean in population 1:
Mean in population 2:
Confidence level:
Use 1 or 2-tailed test: 1 tailed
  2 tailed


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