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SIMULATION 163

Table 7.2
Major Threats to Internal Validity in Different Experimental Designs When Members Are
Randomly Selected and Assigned

Types of Experimental Designs Major Threats to Internal Validity
1. Pretest & posttest with one experimental Testing, history, maturation
group only
2. Posttests only with one experimental Maturation
and one control group
3. Pretest & posttest with one experimental Mortality
and one control group
4. Solomon four-group design Mortality

“true” versus the “placebo” treatment. The entire process was conducted by an
outside testing agency which alone knew who got what treatment. Since both
the experimenter and the subjects are blinded, such studies are called double-
blind studies. Since there is no tampering with the treatment in any way, such
experimental studies are the least biased.
As mentioned previously, managers rarely undertake the study of cause-and-
effect relationships in organizations using experimental designs because of the
inconveniences and disruptions they cause to the system.

Ex Post Facto Designs
Cause-and-effect relationships are sometimes established through what is called
the ex post facto design. Here, there is no manipulation of the independent vari-
able in the lab or field setting, but subjects who have already been exposed to
a stimulus and those not so exposed are studied. For instance, training programs
might have been introduced in an organization 2 years earlier. Some might have
already gone through the training while others might not. To study the effects of
training on work performance, performance data might now be collected for
both groups. Since the study does not immediately follow after the training, but
much later, it is an ex post facto design.
More advanced experimental designs such as the completely randomized
design, randomized block design, Latin square design, and the factorial design
are described in the Appendix to this chapter, for the student interested in these.

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. A simulation can be thought of as an experiment conducted
in a specially created setting that very closely represents the natural environment