Complex Design studying two or more independent variables at the same time Psychology 2300 Chapter 11 Complex Designs Definitions Example using Pennebaker study o Type of writing emotional v superficial o Type of instruction insight v no insight o Create factorial conditions in your experiment where each level of an independent variable is paired with each level of another independent variable Examples and terminology 2 X 2 factorial design see diagram o Two numbers two independent variables o Each factor has 2 levels Example using 2 X 2 factorial design 2 independent variables 2 X 2 1 2 1 2 2 levels per factor 4 conditions cells total Four conditions aka cells 2 x 2 4 Main effect effect of each independent variable on the dependent variable Interaction effect of one independent variable depends on the level of another independent variable o The overall goal of complex design is an interaction Identifying interaction effects Interaction occurs when the effect of one independent variable on the dependent variable differs depending on the level of another independent variable Or interaction occurs when an independent variable alters the effect of another independent variable on a dependent variable Graphing Both independent variables have an effect doesn t count as an interaction For a 2 X 2 factorial design graph the cell means with the dependent variable on the y axis one independent variable on the x axis and two separate lines for the other independent variable o o If the two lines are not parallel converge diverge or cross an interaction exists If the two lines are parallel no interaction exists Subtraction method Way of identifying an interaction o Find the difference between means o When the results lead to a difference of at least one it is likely that an interaction has taken place Relationship between main effects and interactions Possible to have one main effect but no interaction Possible to have one or two main effects and one interaction Possible to have no main effects and still have an interaction Any combination of main effects and interaction effects is possible Interpreting main and interaction effects Main effects have to be described and interpreted carefully when interactions exist Statistical Analysis o Uses F test ANOVA analysis of variance used for complex designs Provides information about statistical significance Effect size o 2 X 2 factorial design will produce 3 F tests Associated with independent variable 1 Associated with independent variable 2 Association with interaction between independent variables 1 and 2