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INTERNAL AND EXTERNAL VALIDITY 149

INTERNAL VALIDITY

Internal validity refers to the confidence we place in the cause-and-effect rela-
tionship. In other words, it addresses the question, “To what extent does the
research design permit us to say that the independent variable A causes a
change in the dependent variable B?” As Kidder and Judd (1986) note, 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. In lab experiments where cause-and-effect relationships are
substantiated, internal validity can be said to be high.
So far we have talked about establishing cause-and-effect relationships within
the lab setting, which is an artificially created and controlled environment. You
might yourself have been a subject taking part in one of the lab experiments
conducted by the psychology or other departments on campus at some time.
You might not have been specifically told what cause-and-effect relationships
the experimenter was looking for, but you would have been told what is called
a “cover story.” That is, you would have been apprised in general terms of
some reason for the study and your role in it, without divulging its true pur-
pose. After the end of the experiment you would also have been debriefed and
given a full explanation of the experiment, and any questions you might have
had would have been answered. This is how lab experiments are usually con-
ducted: Subjects are selected and assigned to different groups through match-
ing or randomization; they are moved to a lab setting; they are given some
details of the study and a task to perform; and some kind of questionnaire or
other tests are administered both before and after the task is completed. The
results of these studies would indicate the cause-and-effect relationship
between the variables under investigation.

EXTERNAL VALIDITY OR GENERALIZABILITY
OF LAB EXPERIMENTS

To what extent would the results found in the lab setting be transferable or gen-
eralizable to the actual organizational or field settings? In other words, if we do
find a cause-and-effect relationship after conducting a lab experiment, can we
then confidently say that the same cause-and-effect relationship will also hold
true in the organizational setting?
Consider the following situation. If in a lab experimental design the groups are
given the simple production task of screwing bolts and nuts onto a plastic frame,
and the results indicate that the groups who were paid piece rates were more
productive than those who were paid hourly rates, to what extent can we then
say that this would be true of the sophisticated nature of the jobs performed in
organizations? The tasks in organizational settings are far more complex, and
there might be several confounding variables that cannot be controlled—for
example, experience. Under such circumstances, we cannot be sure that the
cause-and-effect relationship found in the lab experiment is necessarily likely to