2 Introduction

2.1 Objectives

Aim: To carry out basic one and two sample statistical tests.

By the end of this section and practical participants should be able to achieve the following for each of the listed tests:

1. Understand what the purpose of each test is
2. Perform the test in R
3. Interpret the test output
4. Understand under what assumptions/conditions each test is appropriate
5. Check for those assumptions

The tests covered in this practical are:

1. One-sample tests
   • One sample t-test
   • One-sample Wilcoxon signed-rank test
2. Two-sample tests
   • Student’s t-test
   • Mann-Whitney U test
   • Paired two-sample t-test
   • Wilcoxon signed-rank test

2.2 Background

This practical does not focus on the underlying mathematical theory of the tests although the demonstrators will be happy to answer any questions. For each test there will be a section explaining its purpose, a section explaining how to perform the test in R, a section explaining the results that have been output to the screen, and a section covering the assumptions required to perform the test.