More Than One Independent Variable Laying Out a Factorial Design A Research Example

1. More Than One Independent Variable Laying Out a Factorial Design A Research Example Choosing a Between-Subjects Design

2. A factor is an independent variable. What is a factor? More Than One Independent Variable

3. A factorial design contains more than one independent variable. The effect of psychotherapy (IV1) and antidepressant drugs (IV2) on depression (DV). A two factor experiment is the simplest factorial design. What is a factorial design? More Than One Independent Variable

4. A factorial design can provide information about both treatment and interaction effects. What information can a factorial design provide? More Than One Independent Variable

5. A main effect is the action of a single IV on the DV. There can be as many main effects as independent variables. What is a main effect? What determines the number of main effects in an experiment? More Than One Independent Variable

6. An experimenter studies the effects of exercise intensity (IV1) and duration (IV2) on depression (DV). If exercise intensity or duration separately reduced depression, these would constitute main effects. Provide an example of a main effect in a hypothetical study of exercise and depression. More Than One Independent Variable

7. Perform an appropriate statistical test. How do we determine whether we have main effects in our experiment? More Than One Independent Variable

8. There are 3 independent variables and 18 treatment conditions. In a 2 x 3 x 3 study, how many IVs and treatment conditions are there? More Than One Independent Variable

9. The independent variables were the perpetrator’s gender (male or female), relationship to the child (parent, step-parent, or parent’s partner), and severity of the abuse (neurological damage, broken bones, or bruising). The dependent variable was sentence length. Provide an example of a 2 x 3 x 3 study. More Than One Independent Variable

10. An interaction is the joint effect of two or more IVs on the DV. When there is an interaction, the effect of one IV is different across levels of the other IV. What is an interaction? More Than One Independent Variable

11. If the antidepressant Paxil produced greater reductions in depression in the Cognitive Behavior Therapy (CBT) condition than the Waiting List condition, this would illustrate an interaction between drug and psychotherapy. Provide an example of an interaction. More Than One Independent Variable

12. A higher-order interaction is an interaction among three or more IVs. Interpretation can be difficult when more than three IVs interact in an experiment. What is a higher-order interaction? More Than One Independent Variable

13. A previous hypothetical study examined the effect of a perpetrator’s gender (male or female), relationship to the child (parent, step-parent, or parent’s partner), and severity of the abuse (neurological damage, broken bones, or bruising) on sentencing. Provide an example of a higher-order interaction. More Than One Independent Variable

14. There would be a higher-order interaction if the perpetrator’s gender, relationship to the child, and severity of abuse jointly determined sentence length. Provide an example of a higher-order interaction. More Than One Independent Variable

15. Assign letters (A, B, C) to the independent variables. Identify all unique two- and three- treatment combinations.For three independent variables, these include AB, AC, BC, and ABC. ABC is the higher-order interaction. How many interactions are possible in a study with three IVs? More Than One Independent Variable

16. An interaction qualifies a main effect, warning us that there may be limits or exceptions to the effect of an IV on the DV. When there is an interaction, we must consider both IVs, because the effects of one factor will depend on the levels of the other factor. How does an interaction affect the interpretation of our results? More Than One Independent Variable

17. The factor-labeling method lists the two factors in parentheses after the numerical notation. For example, 2 x 2 (Type of Name x Length of Name). Explain the factor-labeling method. Laying Out a Factorial Design

18. This method lists the two factors and their respective levels after the numerical notation.For example, 2 x 2 (Type of Name: given, nickname x Length of Name: short, long). Explain the factor and levels method. Laying Out a Factorial Design

19. The factor and levels method provides more detailed information about the design than the factor-labeling method. What advantage does the factor and levels method have over the factor-labeling method? Laying Out a Factorial Design

20. A factorial design is more efficient since it combines several one-factor experiments and allows us to study interactions. A factorial design can achieve greater external validity since it can better recreate the complexity of the multivariate environment. Why use a factorial design instead of two separate univariate experiments? A Research Example

21. Practical limitations include: • number of subjects • time • interpretability of results Why should we keep between-subjects designs simple? Choosing a Between-Subjects Design