Sample size calculator

Input and calculation

Alpha two-sided

/ =

Power

Sample size per group

Sample size in group 2

Allocation ratio n₁:n₂ :

Drop-out rate

Press the Calculate button to calculate the sample size.

Options

Calculate
Sample size
Power (output decimal places: )

Advanced
Unequal sample sizes
Account for drop-outs
Bonferroni correction

Sample size for a two-sample Wilcoxon Mann-Whitney U-Test

The sample size and power for the two-sample Wilcoxon Mann-Whitney U-Test are calculated according to Section 3 of [Noether, G. E. (1987). Sample size determination for some common nonparametric tests. Journal of the American Statistical Association, 82(398), 645-647.]

Mean 1

Mean 2

Standard deviation 1

Standard deviation 2

P(X>Y)

Specific options
Calculate P(X>Y) from means and standard deviations assuming normal distributions