Control group

From EvaluationWiki

A group of subjects that is set up in a certain type of experiment in order to be compared, either throughout the experiment or at the end of it, or both, with the 'experimental group' that receives the treatment under investigation. Ideally, the control group is very similar to the experimental group in all respects except for receiving the treatment, so that eventual differences can be reliably ascribed to the treatment: the ultimate matching occurs when the members of each group are identical twins of those in the other group and raised in the same home in the same way; only in this case do we have the genetic characteristics perfectly matched. Next best is when the two groups are matched for certain generally important characteristics such as age and gender and then randomly assigned between the groups; but this only works well when the groups are of a considerable size.