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2.  Allow demonstration of causality ◦ A causes B  Relatively small sample sizes needed ◦ Minimum of 20 per experimental “cell” 1/19/2016Marketing Research2

3.  CAUSE ◦ Independent variable  OUTCOME ◦ Dependent variable 1/19/2016Marketing Research3 CAUSEOUTCOME

4. 1. Temporal ordering of variables 2. Evidence of association (“concomitant) 3. Control of other causal factors 1/19/2016Marketing Research4

5. 5 Laboratory Controlled setting. Field Natural environment, such as a store or mall Setting

6. 6 Internal: The extent to which competing explanations for the findings observed can be ruled out. External: The extent to which the findings will apply to outside persons, settings, and times. Validity

7.  Manipulate variable of interest ◦ Independent variable: IV ◦ (Variable we can control)  Hold all else constant ◦ Extraneous variables  Measure outcome ◦ Dependent variable: DV ◦ (Variable we cannot directly control) 1/19/2016Marketing Research7

8. Researchers at Madigan Army Medical Center examined effectiveness of duct tape on warts. The 51 patients between 3 and 22 were randomly assigned to receive either cryotherapy or duct tape. Patients in the cryotherapy group received a standard 10 second application of liquid nitrogen, repeated every two to three weeks. In the other group, a small piece of duct tape was placed on the patients' warts and patients were told to keep the tape on for six days. At the end of six days, they removed the tape, soaked the area in water, and used an emery board or pumice stone to rub the dead skin off. Warts were successfully removed in 60 percent (15 of 25) of the patients in the cryotherapy group versus 85 percent (22 of 26) of the patients in the duct tape group. The duct tape group reported fewer side effects than cryotherapy group who reported pain and burning at the site. Overall, the researchers found duct tape to be more effective, less painful, and less expensive than freezing. 1/19/2016Marketing Research8

9.  Assignment to condition ◦ Randomly assign subjects to condition OR ◦ Match subjects on variable of interest  Manipulation ◦ Experimental group gets it ◦ Control group does not get it  Measurement of DV ◦ Pretest ◦ Posttest 1/19/2016Marketing Research9

10.  Pretest posttest control group design: ◦ Experimental Group R O 1 X O 2 ◦ Control Group R O 3 O 4  Posttest only control group design: ◦ Experimental Group R X O 1 ◦ Control Group R O 2 1/19/2016Marketing Research10

11.  Design that investigates the effect of two or more independent variables on a dependent variable  Allows testing of interactions and contingent conditions 1/19/2016Marketing Research11

12. Men Women Ad A Ad B 65 7060 Main Effects of Gender Main Effects of Ad > >

13. 100 90 80 70 60 50 40 30 20 10 Ad AAd B Women Men Believability Interaction Between Gender and Advertising Copy

14.  Experimental research is the best way to test causation.  Experimental research is inherently reductionistic.  Complex designs allow the comparison of several factors simultaneously, including interactions. 1/19/2016Marketing Research14

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