How many factors are required for a factorial analysis?
At least two with at least two levels each
What additional questions does a two-way factorial design ask?
- Is there a main effect of levels in either factor A or B? 2. Do the factors act in combination to affect (interact) the DV? (Simple effect)
Which factor (IV level) is represented by the lines on a plot?
The theoretically less important one
What is a disordinal interaction?
Where the lines cross
What is an ordinal interaction?
Where the lines are not parallel, but don’t cross.
Why are two-way factorial designs more economical? 2
- They require less participants than separate experiments 2. Can provide greater power, due to averaging over the other factor
How do factorial designs reveal generalisability?
They show whether a difference of a main effect holds for other levels of the second factor.
What 3 things can factorial designs allow us to understand?
- Dependence of one variable on the other 2. Generalisability of main effects across multiple levels of another factor 3. Changes in impact, due to moderation of one variable on the other
How many interactions can you test in a factorial design?
One for every pair of factors
What is an interaction?
When the simple effect of one factor on the DV depends on the level of the other factor.
Does having a main effect mean there is an interaction? Why?
No. Main and simple effects are independent.
