Experiments are studies involving intervention by the researcher beyond that required for measurement. The usual intervention is to manipulate a variable (the independent variable) and observe how it affects the participants being studied (the dependent variable). An evaluation of the experimental method reveals several advantages: (a) the ability to uncover causal relationships, (b) provisions for controlling extraneous and environmental variables, (c) convenience and low cost of creating test situations rather than searching for their appearance in business situations, (d) the ability to replicate findings and thus rule out idiosyncratic or isolated results, and (e) the ability to exploit naturally occurring events.
Some advantages of other methods that are liabilities for the experiment include (a) the artificial setting of the laboratory, (b) generalizability from non-probability samples, (c) disproportionate costs in select business situations, (d) a focus restricted to the present and immediate future, and (e) ethical issues related to the manipulation and control of human participants.
Consideration of the following activities is essential for the execution of a well-planned experiment:
Select relevant variables for testing.
Specify the levels of treatment.
Control the environmental and extraneous factors.
Choose an experimental design suited to the hypothesis.
Select and assign participants to groups.
Pilot-test, revise, and conduct the final test.
Analyze the data.
We judge various types of experimental research designs by how well they meet the tests of internal and external validity. An experiment has high internal validity if one has confidence that the experimental treatment has been the source of change in the dependent variable. More specifically, a design's internal validity is judged by how well it meets seven threats. These are history, maturation, testing, instrumentation, selection, statistical regression, and experimental mortality. External validity is high when the results of an experiment are judged to apply to some larger population. Such an experiment is said to have high external validity regarding that population. Three potential threats to external validity are testing reactivity, selection interaction, and other reactive factors.
Experimental research designs include (a) preexperiments, (b) true experiments, and (c) quasi-experiments. The main distinction among these types is the degree of control that the researcher can exercise over validity problems. Three preexperimental designs were presented in the chapter. These designs represent the crudest form of experimentation and are undertaken only when nothing stronger is possible. Their weakness is the lack of an equivalent comparison group; as a result, they fail to meet many internal validity criteria. They are the (a) after-only control study, (b) one-group pretest-posttest design, and (c) static group comparison. Two forms of the true experiment were also presented. Their central characteristic is that they provide a means by which we can ensure equivalence between experimental and control groups through random assignment to the groups. These designs are (a) pretest-posttest control group and (b) posttest-only control group. The classical two-group experiment can be extended to multigroup designs in which different levels of the test variable are used as controls rather than the classical nontest control. In addition, the true experimental design can be extended into more sophisticated forms that use blocking. We discuss two such forms, the randomized block and the Latin square, in Appendix 12, along with the factorial design in which two or more independent variables are accommodated. Between the extremes of preexperiments, with little or no control, and true experiments, with random assignment, there is a gray area in which we find quasi-experiments. These are useful designs when some variables can be controlled but equivalent experimental and control groups usually cannot be established by random assignment. There are many quasi-experimental designs, but only three were covered in this chapter: (a) nonequivalent control group design, (b) separate sample pretest-posttest design, and (c) group time series design.
Test marketing is a controlled experimental procedure conducted in a carefully selected marketplace to test a product or service to predict sales and profit outcomes. Marketing managers use test marketing to introduce new products or services, add products to existing lines, identify concepts with potential, or relaunch enhanced versions of established brands. There are six major types of test markets. A standard test market is a traditional test of a product and/or marketing mix variables on a limited geographic basis. It provides a real-world test on a smaller, less costly scale. The firm selects test market cities or regions comparable to those of the intended consumers of the product and tests it through its existing distribution channels. Controlled test markets are "live" forced distribution tests conducted by a specialty research supplier that guarantees distribution of the test product through outlets in selected cities. An electronic test market is a test system that combines store distribution services, consumer scanner panels, and household-level media delivery in specifically designated markets. Retailers and cable TV operators have cooperative arrangements with the research firm in these tests. A simulated test market (STM), often a pretest before a full-scale market test, occurs in a laboratory setting designed to simulate a traditional shopping environment using a sample of the product's consumers. STMs use computer models and data provided by participants in the simulation. A virtual test market uses a computer simulation and hardware to replicate the immersion of an interactive shopping experience in a virtual, threedimensional environment. Web-enabled test markets are a growing trend for large consumer packaged-goods manufacturers that seek fast, cost-effective means to test new products, refine old ones, survey customer attitudes, and build relationships.
