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144 EXPERIMENTAL DESIGNS

transfer all those without the M.Acc. degree currently in the department to other
departments and recruit fresh M.Acc. degree holders to take their place. Such a
course of action is bound to disrupt the work of the entire organization inasmuch
as many new people will have to be trained, work will slow down, employees
will get upset, and so on. However, the hypothesis that possession of a M.Acc.
degree would cause increases in productivity can be tested in an artificially cre-
ated setting (i.e., not at the regular workplace) in which an accounting job can
be given to three groups of people: those with a M.Acc. degree, those without a
M.Acc. degree, and a mixed group of those with and without a M.Acc. degree
(as is the case in the present work setting). If the first group performs exceed-
ingly well, the second group poorly, and the third group falls somewhere in the
middle, there will be evidence to indicate that the M.Acc. degree qualification
might indeed cause productivity to rise. If such evidence is found, then planned
and systematic efforts can be initiated to gradually transfer those without the
M.Acc. degree in the accounting department to other departments and recruit
others with this degree to this department. It is then possible to see to what
extent productivity does, in fact, go up in the department because all the staff
members are M.Acc. degree holders.
As we saw earlier, experimental designs fall into two categories: experiments
done in an artificial or contrived environment, known as lab experiments, and
those done in the natural environment in which activities regularly take place,
known as the field experiment.

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. In other words, the possible effects of other variables on the depen-
dent variable have to be accounted for in some way, so that the actual causal
effects of the investigated independent variable on the dependent variable can
be determined. It is also necessary to manipulate the independent variable so
that the extent of its causal effects can be established. The controls and manip-
ulations are best done in an artificial setting (the laboratory), where the causal
effects can be tested. When controls and manipulations are introduced to estab-
lish cause-and-effect relationships in an artificial setting, we have laboratory
experimental designs, also known as lab experiments.
Because we use the terms control and manipulation, let us examine what
these concepts mean.

CONTROL

When we postulate cause-and-effect relationships between two variables X and
Y, it is possible that some other factor, say A, might also influence the dependent