What is a Control Group?

Definition: A control group is a group of individuals that participate in a given experiment but whom are not exposed to the element being tested. In other words, the group remains neutral to the test.

What Does Control Group Mean?

In any given experiment there must be two groups: a control group and an experimental group. The role of the control group is to provide a baseline result for the test. The group will not be directly or indirectly exposed to the element that is being tested and this neutrality provides a result that will be compared with the results of the experimental group (the one being exposed to the tested element) to examine and compare the deviations between each results.

By having a control group the person in charge of the experiment makes sure the results obtained from the experimental group are actually derived from their exposure to the element of the test. Control group’s individuals should be carefully picked to guarantee they possess similar characteristics with the experimental group individuals. Individuals should share a common profile (like age, gender, among others) and they must be previously screened before being included in the experiment.


A pharmaceutical company is currently testing a muscle relaxer drug for high-performance athletes. The company is currently reviewing the actual relief caused by the drug and the amount of time it takes to start experiencing results, along with possible side effects. In order to perform this experiment the company gathered a group of 30 of these athletes and divided them in Group A (control) and Group B (experimental).

Both groups will be exposed to a 1 hour marathon-type run and after that they will receive a pill they must ingest. Group A will receive a placebo pill and Group B will receive the experimental drug. After the experiment was performed, Group A experienced muscle relief 1 hour after the physical exercise was finished. On the other hand, Group B experienced muscle relief within the first 10 minutes. No side effects were observed after the drugs were administered.

By having a control group the company can conclude that this drug reduces the amount of time it takes to relief muscles after physical activities.