6. Wilcoxon rank-sum test and Wilcoxon signed-rank test
Amy Atkinson
This page is under construction for 24/25 and may be subject to change before the teaching week.
Lecture
Watch lecture Part 1 Watch lecture Part 2 Watch lecture Part 3 Watch lecture Part 4
Download ALL the lecture slides here in both pptx and pdf format.
Post-lecture activity
Lab preparation
Watch the preparation video here
Download the files discussed in the video here
Lab
Download the lab materials here
Overview
I’ll provide you with one or two research questions each week which will require you to complete the statistical tests covered in the lectures.
You can work in groups.
Use the lab preparation video and script, lecture slides, and previous content covered in the statistics modules to help you
Begin the script in the lab and complete in your own time
You can write your script as a .R or Rmd file
Submit for feedback. For this week’s lab, scripts should be submitted on the moodle link by: Friday of Week 16 at 3pm
I’ll provide feedback on a subset of scripts - You will not be judged or marked on your scripts – I’m providing feedback to help you to improve your coding skills and prepare you for your dissertation next year
I’ll also release a model script I’ve written - this will go live on Moodle on Friday of Week 16 at 3pm
Research question 1
You are a researcher interested in whether the old saying “an apple a day keeps the doctor away is true”.
You recruit 16 people and assign each participant to either a “0 apples” or “1 apple” condition. Participants in the “0 apple” condition eat 0 apples every day for a year. Participants in the “1 apple” condition eat 1 apple a day for a year. You ask participants to report how many times they visited the GP in the year.
Research question 2
You are interested in whether eating bananas keeps the doctor away.
This time you recruit only one group of participants. In the first year, you ask them to eat 0 banana every day. In the second year, you ask them to eat 1 bananas a day. You ask them to report how many times they visit the GP in Year 1 and Year 2.
A template for running the Wilcoxon rank-sum test and the Wilcoxon signed-rank test
Your script should aim to answer and interpret both of these research questions
Start a new session on the server.
I have uploaded a .R and .Rmd file to this week’s lab folder. You could use this to get started or just create your own blank .R/.Rmd file
Load packages and data
Normality checks
Explore your data (e.g. descriptive statistics, a plot)
Conduct the statistical test
Calculate an effect size
Interpret your data
Upload your script
You can upload your finished script for feedback on your code here and feedback will be posted onto Moodle.