Using a nonequivalent groups design is an excellent way to control for extraneous variables.

Question

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Nonequivalent groups design does not provide full control over extraneous variables. As the groups are not randomly assigned, there is a possibility of preexisting differences between the groups that can affect the outcome of the study. Therefore, other techniques such as matching, statistical control or randomization should be used in conjunction with this design to increase the control over extraneous variables.

Using a Nonequivalent Groups Design Is an Excellent Way to Control