# Psychology 2080A/B Chapter Notes - Chapter 12: Factorial Experiment

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Published on 22 Apr 2013

Department

Psychology

Course

Psychology 2080A/B

Professor

CHAPTER 12: TRUE EXPERIMENTS, PART 2: FACTORIAL DESIGNS

-often we want to examine the effect of two or more variables in a single

experiment because of :

-efficiency: as long as you are designing an experiment, building

another independent variable into the design may not require much

additional effort

factorial design: research design that involves all combinations of at least

two variables of two or more independent variables

-in the simplest case we have a 2 x 2 factorial

-you can have as many levels but increasing complexity will require more

time to conduct the experiment

Main Effects

main effect: in a factorial experiment the effect of one independent variable

average over all levels of another independent variable

interaction: when the effect of one independent variable depends on the

level of another independent variable

-if graphical representation of a factorial experiment shows curves aren’t

parallel there is an interaction between the variables

-to have interaction if one or the other independent variable has no main

effect or even if neither independent variable has a main effect

Types of Interactions

antagonistic interactions: interaction in which the two independent variables

tend to reverse each others effects

synergistic interaction: interaction in which the two independent variables

reinforce each others effects

ceiling-effect interaction: interaction in which one variable has a smaller

effect when paired with higher levels of a second variable

## Document Summary

Chapter 12: true experiments, part 2: factorial designs. Often we want to examine the effect of two or more variables in a single experiment because of : In the simplest case we have a 2 x 2 factorial. You can have as many levels but increasing complexity will require more time to conduct the experiment. Main effects main effect: in a factorial experiment the effect of one independent variable average over all levels of another independent variable interaction: when the effect of one independent variable depends on the level of another independent variable. If graphical representation of a factorial experiment shows curves aren t parallel there is an interaction between the variables. To have interaction if one or the other independent variable has no main effect or even if neither independent variable has a main effect.