Factorial Between-subjects ANOVA Flashcards
What is a factorial ANOVA?
Between subjects design with multiple IVs
What are benefits of factorial designs?
Look at how variables interact - main effects of IVs
Based on marginals means (means for 1 IV averaged out across all levels of the other IVs)
What is an interaction?
The effect of an IV may depend on the level of of another. An IV has different effect on DV depending on values of another IV
Effect of 2 IVs isn’t additive
What is the main effect of a significant interaction?
Presence of interaction may affect generality (even if significant) - interpret with caution
What does a graph with parallel horizontal lines mean?
Main effect of IV1 and nothing else
What does a graph with 2 non-horizontal parallel lines mean?
Main effects of IV1 and IV2
What does a graph where the lines form a cross mean?
Interaction with no main effects
What are ordinal interactions?
Non-parallel lines sloping in same direction without crossing
Treatment has more intense effect in one condition than another
May be spurious id data is ordinal rather than interval
What is an assumption of ordinal interactions?
Interval data - assume 2 increases are numerically comparable
What are spurious ordinal interactions due to ceiling effects?
One horizontal line on top and sloping line towards top line without crossing underneath
What is a spurious ordinal interaction due to floor effects?
Horizontal bottom line and sloping top line down to bottom line
What are cross over interactions?
1 factor has one effect in one condition and the opposite effect in another condition
Not vulnerable to ordinal data issues
What is the use of post-hocs in factorial ANOVAs?
To interpret main effects
Interactional posthocs aid interpretation of significant interactions - compare cell means across factors
