How to Perform Two-Sample Wilcoxon Rank Sum Test

This article describes how to perform the Wilcoxon rank-sum test to compare the median between two samples.

This test can be applied to two samples of equal or different sizes. For paired samples see Test - Nonparametric - Paired Samples Wilcoxon Test.

Requirements

A Displayr document with a data set.

From the Report tree select + > Advanced Analysis > Test > Nonparametric > Two Sample Wilcoxon Rank Sum Test.
Specify the outcome variable to use under Object Inspector > Data > Two-Sample Wilcoxon Test > Outcome. The outcome variable is the variable whose sample is to be analyzed.
Under Object Inspector > Data > Two-Sample Wilcoxon Test > Group, specify the variable that each observation comes from. When this variable is numeric, it is automatically grouped into approximately equal-sized groups using the median and then converted by the function.

OPTIONAL: You can modify the following settings to adjust the output:

mu - Difference in the median of the two samples, as assumed under the null hypothesis.
Alternative hypothesis - Use a two-sided or one-sided test.
Type of test - Method by which the p-value is computed.
Output
- Summary - Shows a nicely formatted table of the test results (default).
- R - The original text-based output from the wilcox.test function.
Variable names - Display Variable Names in the output, instead of Variable Labels.
More decimal places - Display numeric values with 8 decimal places.