First video that covers most things
- video
- slides
- questions and answers
Second video that covers choosing the correct statistical test for factorial experiments.
- video
- slides
- questions

Objectives
- Understand why researchers use factorial designs
- Understand different kinds of factorial designs and their plusses and minuses
What Students Should Be Able To Do After This Activity
- Identify the design of a study
Prerequisite Knowledge
- understand within vs. between-subject single-variable designs

What Students Should Be Able To Do After This Activity
- Understand what a main effect means and what an interaction means in a 2x2 study
- Identify whether there are main effects and interactions in an experiment with a factorial design
What Students Struggle with
- A confusing aspect is that students are presented only with the means of each group, not the variance around the means. It is impossible to eyeball exactly if the main effects and interaction are or are not significant (p<.05); that is the purpose of having statistical software. So these activities assume a very large sample size, as if the error bars are tiny. This is hard for some students to understand.
- It is important to be able to identify main effects and interactions when presented in line graphs, bar graphs, table, or really any other format. This requires a conceptual understanding of what they mean rather than just knowing a list of steps to follow to determine if there are main effects or interactions.
- Students often jump ahead and assume that they can guess the correct answers about whether or not there are main effects or interactions, but then make mistakes. It is important to actually do the calculations.
- After practice, most students do very well at this on the test.