Presentation on theme: "Exploring Marketing Research William G. Zikmund Chapter 11: Experimental Research."— Presentation transcript:
Exploring Marketing Research William G. Zikmund Chapter 11: Experimental Research
Experiment A research investigation in which conditions are controlled One independent variable is manipulated (sometimes more than one) Its effect on a dependent variable is measured To test a hypothesis
Basic Issues of Experimental Design Manipulation of the Independent Variable Selection of Dependent Variable Assignment of Subjects (or other Test Units) Control Over Extraneous Variables
The experimenter has some degree of control over the independent variable. The variable is independent because its value can be manipulated by the experimenter to whatever he or she wishes it to be.
Experiment Treatment Alternative manipulations of the independent variable being investigated
Independent Variable The experimenter controls independent variable. The variable’s value can be manipulated by the experimenters to whatever they wish it to be.
Manipulation of Independent Variable Classificatory vs. continuous variables Experimental and control groups Treatment levels More than one independent variable
Experimental Treatments The alternative manipulations of the independent variable being investigated
Dependent Variable Its value is expected to be dependent on the experimenter’s manipulation Criterion or standard by which the results are judged
Laboratory ExperimentField Experiment Artificial-Low Realism Few Extraneous Variables High control Low Cost Short Duration Subjects Aware of Participation Natural-High Realism Many Extraneous Variables Low control High Cost Long Duration Subjects Unaware of Participation
Control Groups Isolate extraneous variation
When does an Experiment have Internal Validity? Internal Validity - The ability of an experiment to answer the question whether the experimental treatment was the sole cause of changes in a dependent variable Did the manipulation do what it was supposed to do?
Isolating Extraneous Variation with a Control Group History Effects Maturation Effects Mortality Effects
Type of Extraneous VariableExample History - Specific events in the environment between the Before and After measurement that are beyond the experimenter’s control Maturation - Subjects change during the course of the experiment Testing - The Before measure alerts or sensitizes subject to nature of experiment or second measure. A major employer closes its plant in test market area Subjects become tired Questionnaire about the traditional role of women triggers enhanced awareness of women in an experiment.
Instrument - Changes in instrument result in response bias Selection - Sample selection error because of differential selection comparison groups Mortality - Sample attrition; some subjects withdraw from experiment New questions about women are interpreted differently from earlier questions. Control group and experimental group is self-selected group based on preference for soft drinks Subjects in one group of a hair dying study marry rich widows and move to Florida
How can Internal Validity Increase?
Increasing Internal Validity Control group Random assignment Pretesting and posttesting Posttest only
What are the Different Basic Experimental Designs?
Quasi-Experimental Designs One Shot Design (After Only) One Group Pretest-Posttest Static Group Design
One Shot Design (After Only) XO 1
One Group Pretest-Posttest O 1 X O 2
Static Group Design Experimental GroupX O 1 Control Group O 2
Three Good Experimental Designs Pretest - Posttest Control Group Design Posttest Only Control Group Solomon Four Group Design
Pretest-Posttest Control Group Design Experimental Group R O 1 X O 2 Control Group R O 3 X O 4
Posttest Only Control Group Experimental Group R X O 1 Control Group R O 2