1. Complex Experiments

2. Basic Experiment Simplest experimental design
Two levels of one independent variable
Compares only two groups

3. Increasing the Number of Independent Variables
Manipulate more than one IV
Typically, two or three IV’s are operating simultaneously
- Closer approximation of real-world conditions

4. Factorial Designs Factorial designs More than one IV (or factor)
All levels of each IV are combined with all levels of the other IV’s
Simplest factorial is a 2 X 2 factorial design

5. Berkowitz and LePage (1967)
2 X 2 Factorial Design
Factor A (IV1):
Presence of a Weapon
Level 1 = Gun
Level 2 = Badminton Racket
Factor B (IV2):
Amount of Provocation
Level 1 = High Provocation
Level 2 = Low Provocation
DV: Aggression: Number of shocks delivered

6. Other Factorial Designs
3 X 4 Factorial Design
2 X 3 Factorial Design
2 X 2 X 2 Factorial Design
Identify the number of experimental conditions
in each of these designs.

7. Main Effects and Interactions
Interpretation of Factorial Designs
Two kinds of information
Main effect of an independent variable
Interaction between the independent variables

8. Main Effects and Interactions
A main effect tells us the effect each variable has by itself.
An interaction tells us that the effect of one independent variable depends on the particular level of the other.

9. Brown, Novick, Lord, & Richards (1992)

10. IV x PV Designs
Factorial designs with manipulated and nonmanipulated variables (sometimes called IV x PV designs
Independent variable (IV) x participant variable (PV)
Allows researchers to examine how different individuals respond to the same manipulated IV

11. Orth-Gomer et al. (2000)

12. Between and Within Group Designs
Assignment procedures and factorial designs
Two basic ways of assigning participants to conditions
1. Between (Independent) groups design
2. Within (Repeated measures) design
Combination of the two basic ways is called a mixed factorial design

13. Example: Silverman et al (1978)
Male’s ability at dart-throwing before and after subliminal presentation of a message “Beating Dad is OK”
Poor design:
Before Message
After Message X

14. A better design?