Title: Experimental Designs
1(No Transcript)
2Chapter 12 Experimental Designs
3Chapter Objectives
- understand the role and scope of experimental
research in business - distinguish between causal and correlational
analysis - explain the difference between laboratory and
field experiments - explain the following terms extraneous
variables, manipulation, experimental and control
groups, treatment effect, matching and
randomisation - discuss the seven possible threats to internal
validity in experimental designs - describe the different types of experimental
designs - explain the role of simulation in experimental
research - describe the ethical issues involved in
experimental research
4Experimental Designs
Laboratory Experiment
Field Experiment
Cause - Effect relationships established
by 1. Manipulating treatments 2.
Controlling for external or exogenous
variables Manipulation of Treatment Example
Three different teaching methods given to three
different groups of students Straight lectures
to 10 students simulation only, to another 10
students Both lectures and simulations to 10
other students Assess which results in greatest
amount of learning
5- Simulation alone is ineffective.
- Lectures are more effective than no treatment at
all. - Both lectures and simulation are extremely
effective. - Cause - Effect relationship can be established
because of - Controls for age, etc. through either
randomisation or matching of groups - Because of an additional control group
6- Control of Exogenous Variables through
- Random assignment of members to various groups
- Matched groups
- Control groups
- Example Different treatments may have different
effects on people with differing interests, ages,
expertise,etc. - So, a) randomly assign members to different
treatment groups. The differences will be
randomly distributed. Systematic bias will be
reduced. - b) match the different groups as closely as
possible in terms of age, interest, expertise,
etc. - c) have an additional control group of students
who ar not exposed to any of the three
treatments, and see how they learn and compare.
7Controlled Variables
Variables that might affect the Cause - Effect
relationship among the IVs and DV, and hence need
to be controlled. Example 1. Age 2. Education
levels 3. Length of Service in
Organisation Might affect the relationship
between job characteristics and job satisfaction
8Uncontrolled Variables
Variables or phenomena that occur unexpectedly
and can confound the results. Example
Advertising
Purchasing
(IV)
(DV)
Sudden Unemployment
(Uncontrolled Variable)
(Controlled Variables)
9-
- Lab Experiements can have tight controls and
hence the validity of cause Effect findings is
high ie., they have high internal validity. But
their generalisability to real life is low,
because of their tight controls ie., their
external validity is low. - Field Experiments (eg, different incentive plans
(treatment0 in work organisations for assessing
effect on productivity, have high external
validity or generalisability (because they
represent the actual situations), but have low
internal validity (ie., cause effect
relationships are contaminated because of no
controls.)
10Cause and effect relationship after randomisation
11- FACTORS AFFECTING INTERNAL VALIDITY
- HISTORY EFFECTS
- MATURATION EFFECTS
- TESTING EFFECTS
- INSTRUMENTATION EFFECTS
- SELECTION BIAS
- STATISTICAL REGRESSION
- MORTALITY
12History effects inexperimental design
13Maturation effects on the cause and effect
relationship
14Pre-test and post-test experimental group design
15Post-test only with experimental and control
groups
Treatment effect (O1 - O2)
16Pre-test and post-test experimental and control
groups
Treatment effect (O2 - O1) (O4 - O3)
17Solomon four-group design
Treatment effect (E) could be judged by E 1
(O2 - O1) E 2 (O2 - O4 ) E 3 (O5 - O6) E 4
(O5 - O3 ) E 5 (O2 - O1) (O4 - O3 ) If
all Es are similar, the cause and effect
relationship is highly valid.
18Major threats to internal validity in different
experimental designs
19Simulation as experimentation
20Example of a managementflight simulator
21Ethical Issues in Experimental Research
- The following practices are considered unethical
- pressuring individuals to participate in
experiments through coercion or applying social
pressure - giving out menial tasks and asking demeaning
questions that diminish the subjects
self-respect - deceiving subjects by deliberately misleading
them as to the true purpose of the research - exposing participants to physical or mental
stress - not allowing subjects to withdraw from the
research when they want to
22Ethical Issues in Experimental Research(contd)
- using the research results to disadvantage the
participants, or for purposes that they would not
like - not explaining the procedures to be followed in
the experiment - exposing respondents to hazardous and unsafe
environments - not debriefing participants fully and accurately
after the experiment is over - not preserving the confidentiality of the
information given by the participants - withholding benefits from control groups
23Decision points for embarking on an experimental
design
24A completely randomised design
25A randomised block design
Blocking factor residential areas
Note that the Xs above indicate only various
levels of the blocking factor, and the Os (the
number of passengers before and after each
treatment at each level) are not shown, although
these measures will be taken.
26The Latin square design
Day of the week
27A 3 3 factorial design
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