What is the difference between a comparison group and a control group?
From PsychWiki - A Collaborative Psychology Wiki
The difference between a comparison group and a control group can be seen in the way a comparison group is exposed to all of the same conditions as the experimental group, except for the variable being tested, while a control group is not exposed to any condition. The comparison group is more similar to the experimental group than the control group because the comparison group is exposed to the same conditions, except the experimental condition, while the control group is simply observed.
Example / Application
Example: Control Group
Application: In this video on how to conduct an experiment, the concept of a control group is explained. In the case of the video, they are conducting an experiment to test their hypothesis that highway 101 is the quickest way to get from San Jose to San Fransisco. In order to have this hypothesis tested, the experiment needs a control group (a different highway) to compare to the hypothesized quickest route. This experiment has a control group and not a comparison group because the highway is not being exposed to the same conditions as highway 101, it is simply being observed as to which is the fastest route.