Chapter 13. The Wilcoxon Rank-Sum Test

  • 13.1 Introduction 263

  • 13.2 Synopsis 263

  • 13.3 Examples 265

  • 13.4 Details & Notes 270

13.1 Introduction

The Wilcoxon rank-sum test is a non-parametric analog of the two-sample t-test (Chapter 5). It is based on ranks of the data, and is used to compare location parameters, such as the mean or median, between two independent populations without the assumption of normally distributed data.

Although the Wilcoxon rank-sum test was developed for use with continuous numeric data, the test is also applied to the analysis of ordered categorical data. In clinical data analysis, this test is often useful, for example, for comparing patient global assessments or disease severity ratings between two treatment groups.

13.2 Synopsis ...

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