Question

Consider an experiment with four independent variables: A, B, C, and D.

Factor A has 3 levels and is a between-subjects variable; Factor B has 2 levels and is a within-subjects variable; Factor C has 2 levels and is a between-subjects variable; Factor D has 3 levels and is a within-subjects variable.

1. How many “cells” or “conditions” or “groups” are there in this experiment?

2. If you want to test 10 participants per cell, how many TOTAL participants will you need?

3. Identify ALL of the effects to be tested via ANOVA

Answer 1

A mixed ANOVA compares the mean differences between groups that have been split on two "factors" (also known as independent variables), where one factor is a "within-subjects" factor and the other factor is a "between-subjects" factor. For example, a mixed ANOVA is often used in studies where you have measured a dependent variable (e.g., "back pain" or "salary") over two or more time points or when all subjects have undergone two or more conditions (i.e., where "time" or "conditions" are your "within-subjects" factor), but also when your subjects have been assigned into two or more separate groups (e.g., based on some characteristic, such as subjects' "gender" or "educational level", or when they have undergone different interventions). These groups form your "between-subjects" factor. The primary purpose of a mixed ANOVA is to understand if there is an interaction between these two factors on the dependent variable. Before discussing this further, take a look at the examples below, which illustrate the three more common types of study design where a mixed ANOVA is used.