Business Research Methods William G. Zikmund

1. Business Research MethodsWilliam G. Zikmund Chapter 12: Experimental Research

2. 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

3. 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

4. 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.

5. Experiment Treatment Alternative manipulations of the independent variable being investigated

6. Independent Variable • The experimenter controls independent variable. • The variable’s value can be manipulated by the experimenters to whatever they wish it to be.

7. Manipulation of Independent Variable • Classificatory Vs. continuous variables • Experimental and control groups • Treatment levels • More than one independent variable

8. Experimental Treatments • The alternative manipulations of the independent variable being investigated

9. Dependent Variable • Its value is expected to be dependent on the experimenter’s manipulation • Criterion or standard by which the results are judged

10. Dependent Variable • Selection • e.g... sales volume, awareness, recall, • Measurement

11. Test Units • Subjects or entities whose response to the experimental treatment are measured or observed.

12. Two Types of Experimental Error • Constant errors • Random errors

13. Field versus Laboratory Experiments

14. Controlling Extraneous Variables • Elimination of extraneous variables • Constancy of conditions • Order of presentation • Blinding • Random assignment

15. How May an Experimenter control forExtraneous Variation? • Eliminate Extraneous Variables • Hold Conditions Constant • Randomization • Matching Subjects

16. Establishing Control

17. Demand Characteristics • Experimental procedures that intentionally hint to subjects something about the experimenter’s hypothesis

18. Demand Characteristics • Guinea pig effect • Hawthorne effect

19. Field Vs. Laboratory Experiment

20. Laboratory Experiment Field Experiment Artificial-Low Realism Natural-High Realism Few Extraneous Variables Many Extraneous Variables High control Low control Low Cost High Cost Short Duration Long Duration Subjects Aware of Participation Subjects Unaware of Participation

21. Control Groups Isolate extraneous variation

22. 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?

23. Factors Influencing Internal Validity • History • Maturation • Testing • Instrumentation • Selection • Mortality

24. Isolating Extraneous Variationwith a Control Group • History Effects • Maturation Effects • Mortality Effects

25. Type of Extraneous Variable Example 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.

26. 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 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

27. How can Internal Validity Increase?

28. IncreasingInternalValidity • Control group • Random assignment • Pretesting and posttesting • Posttest only

29. What are the Different Basic Experimental Designs?

30. Quasi-Experimental Designs • One Shot Design (After Only) • One Group Pretest-Posttest • Static Group Design

31. One Shot Design (After Only) X O1

32. One Group Pretest-Posttest O1 X O2

33. Static Group Design Experimental Group X O1 Control Group O2

34. Three Good Experimental Designs • Pretest - Posttest Control Group Design • Posttest Only Control Group • Solomon Four Group Design

35. Pretest-Posttest Control Group Design Experimental Group R O1 X O2 Control Group R O3 X O4

36. Posttest Only Control Group Experimental Group R X O1 Control Group R O2

37. History weak Maturation weak Testing not relevant Instrumentation not relevant Selection weak Mortality weak One-Shot DesignInternal Validity Problems

38. History weak Maturation weak Testing weak Instrumentation weak Selection controlled Mortality controlled One-Group Pretest-PosttestInternal Validity Problems

39. History controlled Maturation possible source of concern Testing controlled Instrumentation controlled Selection weak Mortality weak Static-Group DesignInternal Validity Problems

40. History controlled Maturation controlled Testing controlled Instrumentation controlled Selection controlled Mortality controlled Pretest-Posttest ControlInternal Validity Problems

41. History controlled Maturation controlled Testing controlled Instrumentation controlled Selection controlled Mortality controlled Solomon Four-Group DesignInternal Validity Problems

42. History controlled Maturation controlled Testing controlled Instrumentation controlled Selection controlled Mortality controlled Posttest-Only ControlInternal Validity Problems

43. Solomon Four Group Design Experimental Group 1: R O1 X O2 Control Group 1: R O3 O4 Experimental Group 2: R X O5 Control Group 2: R X O6

44. Advanced Experimental Designs are More Complex • Completely randomized • Randomized block design • Latin square • Factorial

45. Completely Randomized Design • An experimental design that uses a random process to assign subjects (test units) and treatments to investigate the effects of only one independent variable.

46. Completely Randomized Designs Control: no music Experimental treatment: slow music Experimental treatment: fast music Average minutes shopper spends in store 16 18 12

47. Independent Variable A Level 1 Level 2 Level 3 Group A Group B Group C

48. Completely Randomized Design With a pretest posttest Group A R O1 X1 O2 Group A R O3 X2 O4 Group A R O5 X3 O6

49. Completely Randomized Design With a posttest Group A R X1 O1 Group B R X2 O2 Group C R X3 O3

50. Randomized Block Design • An extension of the completely randomized design in which a single extraneous variable that might affect test units’ response to the treatment has been identified and the effects of this variable are isolated by blocking out its effects.