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Business Research Methods William G. Zikmund

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Title: 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 variables 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
    experimenters 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
Establishing Control
15
  • Physical Control
  • Holding the value or level of extraneous
    variables constant throughout the course of an
    experiment.
  • Statistical Control
  • Adjusting for the effects of confounding
    variables by statistically adjusting the value of
    the dependent variable for each treatment
    conditions.
  • Design Control
  • Use of the experimental design to control
    extraneous causal factors. Eg. Demand

16
Demand Characteristics
  • Experimental procedures that intentionally hint
    to subjects something about the experimenters
    hypothesis

17
Demand Characteristics
  • Guinea pig effect
  • Hawthorne effect

18
Field Vs. Laboratory Experiment
19
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
20
Control Groups
  • Isolate extraneous variation

21
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?

22
Factors Influencing Internal Validity
  • History
  • Maturation
  • Testing
  • Instrumentation
  • Selection
  • Mortality

23
Isolating Extraneous Variationwith a Control
Group
  • History Effects
  • Maturation Effects
  • Mortality Effects

24
Type of Extraneous Variable
Example
History - Specific events in the environment
between the Before and After measurement that are
beyond the experimenters 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.
25
New questions about women are interpreted differen
tly 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
26
How can Internal Validity Increase?
27
Increasing Internal Validity
  • Control group
  • Random assignment
  • Pretesting and posttesting
  • Posttest only

28
What are the Different Basic Experimental Designs?
29
Quasi-Experimental Designs
  • One Shot Design (After Only)
  • One Group Pretest-Posttest
  • Static Group Design

30
One Shot Design (After Only) X O1
31
One Group Pretest-Posttest O1 X O2
32
Static Group Design Experimental Group X O1
Control Group O2
33
Three Good Experimental Designs
  • Pretest - Posttest Control Group Design
  • Posttest Only Control Group
  • Solomon Four Group Design

34
Pretest-Posttest Control Group Design
Experimental Group R O1 X O2 Control
Group R O3 O4
35
Posttest Only Control Group
Experimental Group R X O1 Control
Group R O2
36
One-Shot DesignInternal Validity Problems
  • History
  • weak
  • Maturation
  • weak
  • Testing
  • not relevant
  • Instrumentation
  • not relevant
  • Selection
  • weak
  • Mortality
  • weak

37
One-Group Pretest-PosttestInternal Validity
Problems
  • History
  • weak
  • Maturation
  • weak
  • Testing
  • weak
  • Instrumentation
  • weak
  • Selection
  • controlled
  • Mortality
  • controlled

38
Static-Group DesignInternal Validity Problems
  • History
  • controlled
  • Maturation
  • possible source of concern
  • Testing
  • controlled
  • Instrumentation
  • controlled
  • Selection
  • weak
  • Mortality
  • weak

39
Pretest-Posttest ControlInternal Validity
Problems
  • History
  • controlled
  • Maturation
  • controlled
  • Testing
  • controlled
  • Instrumentation
  • controlled
  • Selection
  • controlled
  • Mortality
  • controlled

40
Solomon Four-Group DesignInternal Validity
Problems
  • History
  • controlled
  • Maturation
  • controlled
  • Testing
  • controlled
  • Instrumentation
  • controlled
  • Selection
  • controlled
  • Mortality
  • controlled

41
Posttest-Only ControlInternal Validity Problems
  • History
  • controlled
  • Maturation
  • controlled
  • Testing
  • controlled
  • Instrumentation
  • controlled
  • Selection
  • controlled
  • Mortality
  • controlled

42
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
O6
43
Advanced Experimental Designs are More Complex
  • Completely randomized
  • Randomized block design
  • Latin square
  • Factorial

44
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.

45
Completely Randomized Designs
Control no music
Experimental treatment slow music
Experimental treatment fast music
Average minutes shopper spends in store
16 18 12
46
Independent Variable A
Level 1
Level 2
Level 3
Group A
Group B
Group C
47
Completely Randomized Design
With a pretest posttest
Group A R O1 X1 O2 Group B R O3 X2 O4 Group
C R O5 X3 O6
48
Completely Randomized Design
With a posttest
Group A R X1 O1 Group B R X2 O2 Group
C R X3 O3
49
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.

50
Randomized Block Design
Independent Variables
Control no music
Experimental treatment slow music
Experimental treatment fast music
Mornings and afternoons Evening hours
Blocking variable
51
Factorial Design
  • An experiment that investigates the interaction
    of two or more variables on a single dependent
    variable.

52
Independent Variable 1
Slow Music
Fast Music
No Music
No Music cart signs
Independent Variable 2
Grocery cart signs
53
Factorial Design -- Roller Skates
Package Design
Price Red Gold 25 Cell 1 Cell 4 30 Cell
2 Cell 5 35 Cell 3 Cell 6
54
Effects
  • Main effect
  • The influence of a single independent variable on
    a dependent variable.
  • Interaction effect
  • The influence on a dependent variable by
    combinations of two or more independent variables.

55
2 x 2 Factorial Design
Ad A Ad B
Men Women
65 65
Main Effects of Gender
gt
70 60
gt
Main Effects of Ad
56
Interaction Between Gender and Advertising Copy

57
Independent Variable 1
Level 1 Level 2
Level 1 Level 2
Group A
Group B
Independent Variable 2
Group D
Group C
58
2 x 2 Factorial with a Pretest Posttest
Group A R O1 X11 O2 Group B R O3 X21 O4 Group
C R O5 X12 O6 Group D R O7 X22 O8
59
2 x 2 Factorial Design with a Posttest Measure
Group A R X11 O1 Group B R X21 O2 Group
C R X12 O3 Group D R X22 O4
60
A Test Market Experiment on Pricing
Sales in Units (thousands)
Regular Price .99 130 118 87 84 X1104.75 X119
.58
Reduced Price .89 145 143 120 131 X2134.75
Cents-Off Coupon Regular Price 153 129 96 99 X1
119.25
Test Market A, B, or C Test Market D, E, or
F Test Market G, H, or I Test Market J, K, or
L Mean Grand Mean
61
Latin Square Design
  • A balanced, two-way classification scheme that
    attempts to control or block out the effect of
    two or more extraneous factors by restricting
    randomization with respect to the row and column
    effects.

62
1 2 3 1 A B C 2 B C A 3 C A B
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