A new physical therapy is being tested in an experimental setting to see if
the new methods reduce the recovery time for patients who recently
underwent surgery for a torn ACL, a ligament in your knee. To do this, the
researchers in the study first performed intake on participants by observing
their Body Mass Index (BMI) and had them take a survey to describe their
diet and their exercise habits.
Then, the participants were split into three groups: the first group received
no physical therapy, the second group received traditional physical therapy,
and the third group received the new experimental physical therapy.
The group which receives no physical therapy would best be described as
which of the following?

Explanatory Variable
Response Group
Experimental Unit
Control Group

A control group, in research, is a group that is not experimented by the researchers in an experiment. A control group is the opposite of an experimental group, on which the independent variable is performed. In other words, an independent variable is held on 'control' in control group.

In the given scenario, the experiment is being performed to test a new physical therapy. To do so, the researchers divided the group in three groups, in which, one group did not receive any treatment; the treatment is held on 'control' in this group.

So, according to the definition provided, the group that did not receive the treatment will be called a control group, thus the correct answer.