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Marketing Research 5/24/2017 1 Allow demonstration of causality ◦ A causes B Relatively small sample sizes needed ◦ Minimum of 20 per experimental “cell” Marketing Research 5/24/2017 2 CAUSE ◦ Independent variable OUTCOME ◦ Dependent variable CAUSE OUTCOME Marketing Research 5/24/2017 3 1. Temporal ordering of variables 2. Evidence of association (“concomitant covariation”) 3. Control of other causal factors Marketing Research 5/24/2017 4 Setting •Laboratory •Controlled setting. •Field •Natural environment, such as a store or mall 5 Validity 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. 6 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) Marketing Research 5/24/2017 7 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. Marketing Research 5/24/2017 8 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 Marketing Research 5/24/2017 9 Pretest posttest control group design: ◦ Experimental Group R O 1 X O2 ◦ Control Group R O3 O4 Posttest only control group design: ◦ Experimental Group R X O1 ◦ Control Group R O2 Marketing Research 5/24/2017 10 Design that investigates the effect of two or more independent variables on a dependent variable Allows testing of interactions and contingent conditions Marketing Research 5/24/2017 11 Ad A Ad B Men 65 Main Effects > of Gender Women 65 70 60 Main Effects of Ad 100 90 Interaction Between Gender and Advertising Copy 80 70 60 50 40 30 20 10 Ad A Ad B 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. Marketing Research 5/24/2017 14 Marketing Research 5/24/2017 15