Summary of the Experimental
Design
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Random Assignment:
Assigning subjects to conditions by chance, thus minimizing preexisting
differences between those in the different groups. RA is a control technique and must be used in true
experiments.
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Experimental Condition (group): The condition that exposes the subjects
to one version of the IV; the group that receives the experimental treatment.
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Control Condition (group):
A condition identical to the experimental condition, except the version
of the IV is different (often, it is absent). Including a control group is a control technique.
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Independent Variable (IV):
The factor (variable) that you manipulate; the treatment itself.
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Dependent Variable (DV):
The behavior that is measured; the factor that might be affected by
changes in the independent variable.
o Operational Definitions: The
specific techniques used to manipulate the IV and measure the DV.
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Confounding Variables: Any
variable other than the IV that may have an effect on the DV. The goal is to eliminate (control) the
confounding variables using control techniques.
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Control Techniques: Methods used to eliminate confounding variables and
thus, increase Internal Validity.
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Internal Validity: The
degree to which you can infer that a cause and effect relationship exists
between the IV and DV (i.e., that the manipulation of the IV caused a change in
the DV).