Chapter 12: Factorial Designs, 2 IVs Flashcards
Interaction Effect
Whether the effect of the original independent variable depends on the level of another independent variable
E.g. does impairment by talking on phone depend on age
Factorial Design
Two or more independent variables
Study each possible combination of independent variables
E.g. young drivers using cell phones vs not, old drivers using cell phones vs not
Study manipulated & participant variables
Participant Variable
Variable whose levels are selected and not manipulated
E.g. age
Not truly independent variables, but can be called them in factorial designs
Main Effects
Is there an overall difference?
Overall effect of one independent variable on the dependent variable (simple difference)
Two main effects in factorial designs (one effect with each independent variable)
Marginal Means
Arithmetic means for each level of independent variable, averaging over levels of the other independent variable
E.g. calculate average of all people braking time with cell phone and average of all people without cell phone
Interaction
Is there a difference in differences
Crossover interaction & spreading interaction
Crossover Interaction
Effect of IV1 on DV is positive at one level of IV2 but negative at another level of IV2
Direction of relationship changes
Spreading Interaction
Effect of IV1 on DV is stronger at one level of IV2 than at another level of IV 2
Strength of relationship changes
Independent-Groups Factorial Design
AKA between subjects factorial design
Different participants exposed to each level/condition
Both independent variables are studied as independent groups
E.g. in a 2x2 design there are four different groups of participants
E.g. light men drank placebo and alcohol, heavy men drink placebo and alcohol
Within-Groups Factorial Design
AKA repeated measures factorial
All participants exposed to all levels/conditions
Both independent variables are manipulated as within-groups
E.g. in a 2x2 design one group of all participants completes all four combinations
E.g. all participants exposed to alcohol and plant pictures and both aggression and neutral words
Efficient use of participants
Ensures that people in each condition are similar as possible (because they are the same people)
Have to counterbalance the order of photo and word presentation
Mixed Factorial Design
One independent variable is manipulated as independent-groups and the other is manipulated within-groups
E.g. age as independent-groups participant variable (one group young and the other old)
E.g. cell phone condition was manipulated as within groups (each participant drove in both cell phone and no cell phone condition
Three Independent Variables
Three way designs increase the number of differences to be investigated
Three main effects (one for each independent variable)
Three two way interactions
One three way interaction
Three way interactions: are the two way interactions different
E.g. interaction between age, cell phone condition, and traffic condition
If significant, means that the two way interaction dependents on the level of the third independent variable