The tool uses the critical value tables when ni ≤ 20 and a normal approximation for a larger sample size
When ni ≤ 20 the normal distribution chart is only for demonstration.
Unlike t-test that compares the means, the Mann-Whitney U test compares a randomly selected value from group1 to a randomly selected value from group1.
When the two distributions have a similar shape you can use the test to compare also the medians.
When the two distributions have a similar symmetrical shape, you can use the test to compare also the means.
Header: You may change groups' name to the real names.
Data: When entering data, press Enter after each value.
You may copy data from Excel, Google sheets or any tool that separate data with Tab and Line Feed.
Copy the data, one block of consecutive columns includes the header, and paste below. . click to see example: