This document discusses factors that can threaten the internal and external validity of experimental research designs. It identifies six main threats to internal validity: history effects, maturation effects, instrumentation effects, selection bias, statistical regression, and mortality. It also discusses how randomization and matching groups can help control for contaminating variables. The trade-off between internal and external validity is addressed, as well as types of experimental designs, simulation as an alternative, and ethical issues.

1. Chapter 7

2. AnggotaKelompok:
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3. THE LAB EXPERIMENT
As stated earlier, when a cause-and-
effect relationship between an independent
and a dependent variable of interest is to be
clearly established, then all other variables
that might contaminate or confound the
relationship have to be tightly controlled.

4. CONTROL
The manager cannot prove that the
special training alone caused greater
effectiveness, since the previous intermittent
experience of some secretaries with the web
is a contaminating factor. If the true effect of
the train- ing on learning is to be assessed,
then the learners‘ previous experience has
to be controlled.

5. MANIPULATION OF THE
INDEPENDENT VARIABLE
certain manipulations need to be tried. Manipulation
simply means that we create different levels of the
independent variable to assess the impact on the
dependent variable

6. CONTROLLING THE CONTAMINATING
EXOGENOUS OR “NUISANCE” VARIABLES
• Matching Groups
• Randomization

7. CONTROLLING THE CONTAMINATING EXOGENOUS OR
“NUISANCE” VARIABLES
Matching Groups
One way of
controlling the
contaminating or
―nuisance‖
variables is to
match the various
groups by picking
the confounding
characteristics and
deliberately
 Randomization
Another way of controlling the
contaminating variables is to
assign the 60 mem- bers
randomly (i.e., with no
predetermination) to the four
groups. That is, every member
would have a known and equal
chance of being assigned to
any of these four groups
 Advantages of Randomization
that in the former case
individuals are deliberately and
consciously matched to control

8. INTERNAL VALIDITY
• Internal validity refers to the confidence we
place in the cause-and-effect relationship in
research with high internal validity, we are
relatively better able to argue that the
relationship is causal, whereas in studies with
low internal validity, causality can- not be
inferred at all.

9. EXTERNAL VALIDITY OR GENERALIZABILITY OF
LAB EXPERIMENTS
• Representasi the results of the investigation or can
the results of the invrstigation in generalitation.

10. THE FIELD EXPERIMENT
A field experiment, as the name implies, is an
experiment done in the natural envi- ronment in
which work goes on as usual, but treatments are
given to one or more groups

11. External validity and internal validity
External validity refers
to the extent of
generalizability of the
results of a causal study
to other settings,
people, or events
Internal valid-ity refers
to the degree of our
confidence in the causal
effects (i.e., that
variable X causes
variable Y)

12. TRADE-OFF BETWEEN INTERNAL AND
EXTERNAL VALIDITY
• There is thus a trade-off between internal
validity and external validity. If we want high
internal validity, we should be willing to settle
for lower external validity and vice versa.
These problems of external validity usually
limit the use of lab experiments in the
management area. Field experiments are also
infre- quently undertaken because of the
resultant unintended consequences—person-
nel becoming suspicious, rivalries and
jealousies being created among departments,

13. FACTORS AFFECTING INTERNAL VALIDITY
• History Effects
• Maturation Effects
• Testing Effects
• Instrumentation Effects
• Selection Bias Effects
• Statistical Regression
• Mortality

14. History Effects
Certain events or factors that would have an
impact on the independent variable
dependent variable relationship might
unexpectedly occur while the experiment
is in progress, and this history of events
would confound the cause and effect
relationship between the two variables, thus
affecting the internal validity.

15. Maturation Effects
The maturation effects are a function of
the processes both biological and
psychological operating within the
respondents as a result of the passage of
time.

16. Testing Effects
• Frequently, to test the effects of a
treatment, subjects are given what is
called a pr etest (say, a short questionnaire
eliciting their feelings and attitudes). That
is, first a measure of the dependent
variable is taken (the pretest), then the
treatment given, and after that a second
test, called the posttest, administered.

17. Instrumentation Effects
• Instrumentation effects are yet another
source of threat to internal validity. These
might arise because of a change in the
measuring instrument between pretest and
posttest, and not because of the
treatment‘s differential impact at the end
(Cook & Campbell, 1979a).

18. Selection Bias Effects
• The threat to internal validity could also
come from improper or unmatched
selection of subjects for the experimental
and control groups.

19. Statistical Regression
• The effects of statistical regression are
brought about when the members chosen
for the experimental group have extreme
scores on the dependent variable to begin
with.

20. Mortality
• Another confounding factor on the cause-
and-effect relationship is the mortality or
attrition of the members in the
experimental or control group or both, as
the experiment progresses.

21. IDENTIFYING THREATS TO INTERNAL VALIDITY
1) History Effects
2) Maturation.
3) Instrumentation.
4) Selection Bias
5) Statistical Regression
6) Mortality

22. INTERNAL VALIDITY IN CASE STUDIES
If there are several threats to internal validity
even in a tightly controlled lab
experiment, it should become quite clear why
we cannot draw conclusions
about causal relationships from case studies
that describe the events that
occurred during a particular time.

23. FACTORS AFFECTING EXTERNAL VALIDITY
external validity raises issues about the
generalizability of the findings to other settings.

24. REVIEW OF FACTORS AFFECTING INTERNAL
AND EXTERNAL VALIDITY
In summary, at least seven contaminating factors
exist that might affect the internal validity of
experimental designs. Threats to external validity
can be combated by creating experimental
conditions that are as close as possible to the
situations to which the results of the experiment
are to be generalized.

25. TYPES OF EXPERIMENTAL DESIGNS AND
INTERNAL VALIDITY
• Quasi-Experimental Designs
• True Experimental Designs
• Solomon Four-Group Design and Threats to Internal Validity
• Double-Blind Studies
• Ex post facto designs

26. SIMULATION
An alternative to lab and field experimentation
currently being used in business research is
simulation. Simulation uses a model-building
technique to determine the effects of changes,
and computer-based simulations are becoming
popular in business research.

27. ETHICAL ISSUES IN EXPERIMENTAL DESIGN
RESEARCH
The last item is somewhat controversial as to whether
or not it should be an ethical dilemma, especially in
organizational research.

28. MANAGERIAL IMPLICATIONS
• Before using experimental designs in research
studies, it is essential to consider whether
they are necessary at all, and if so, at what
level of sophistication