Overview

Two-way ANOVA

So far you have learnt how to use and interpret the general linear model when:

• the x variable was continuous
• the x variable was categorical with two groups
• the x variable was categorical with two or more groups

This week we will extend of our understanding by learning how to include two categorical explanatory variables in a general linear model. This model is often known as the two-way ANOVA. It allows us to design experiments to test whether a response is influenced by two variables and whether those two variables act independently on the response or interact in some way.

Learning objectives

The successful student will be able to:

• combine dataframes of the same structure

• select, appropriately, two-way ANOVA

• apply and interpret lm() for a two-way ANOVA

• evaluate whether the assumptions of lm() are met

• understand the meaning of the interaction term

• scientifically report a two-way ANOVA result including appropriate figures

Instructions

1. Prepare

   1. 📖 Read Two-way ANOVA

2. Workshop

   1. 💻 Two-way ANOVA Choline deficiency on neuron size

3. Consolidate

   1. 💻 Appropriately test whether there are regional differences between two species of butterfly.