In a well designed experiment it is important that the
experimental group be controlled in such a way as to insure that a single variable be
modified and that the resulting changes due to those modifications can be observed
accurately. The variable which the researcher wishes to alter is the "independent
variable" and the one which is changed do to those modifications is the "dependent
variable."
To make sure that the only thing which is
causing changes in the dependent variable is changes in the independent variable, it is
important to have a control group. The control group is identical to the experimental
group in every way with the exception that the independent variable will not be
modified. This allows the researcher to compare any changes in the experimental group
to the control group to verify that the changes were caused by the experiment and not by
other factors.
In the sited experiment it is apparent that
the researcher is studying the effects of the drug on lung function by monitoring
reductions in stress from walking. The control group should be as close to the
experimental group as possible in every way including health conditions and distance
walked with the exception of using the drug. The experimental group would be given a
regular repeated dosage and the control would not be given the
drug.
One of the two factors which could be studied in both
groups would be the patient's blood pressure as it could be reduced by either the drug,
the walking, or a combination of both. The second factor would be the ease of walking
as walking could get easier due to increased fitness because of walking every day, the
drug, or a combination of the both.
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