Biostats Calculator

Features > Mann-Whitney U test

The Mann-Whitney U test (or Rank-Sum test) is used to compare two groups of samples to see if there is a significant difference.

Unlike the unpaired t-test, it is non-parametric and does not require the data to be normally distributed, or even continuous. It can also distinguish between groups with the same mean but different distributions.

After selecting Mann-Whitney U from the menu, simply enter the values for each sample. Biostats Calculator will compare the distributions of the groups and perform a hypothesis test to determine whether there is a statistically significant difference.

Biostats Calculator reports:

• The median and range of each group's samples
• The p value, indicating how likely it is that the observed difference would occur due to chance alone
• whether the result is significant at the 95% confidence level
• The U statistic which describes the magnitude of variation between samples

Biostats Calculator can perform this test and 11 others from the convenience of your iPhone or iPod Touch. Buy it today!

Related tests

• Unpaired t-test - a more powerful parametric test applicable if the populations being sampled are normally distributed
• Wilcoxon signed-rank test - if you have pairs of repeated samples from the same subjects