no-treatment control group
a control group whose members are not exposed to any experimental manipulation or intervention, thus serving as a neutral comparison for study groups receiving the treatment under investigation. For example, a researcher investigating the effectiveness of a new antidepressant might divide participants into a treatment group that receives the new medication and a separate no-treatment control group that receives no medication whatsoever, and then compare the outcomes of each group to identify any significant differences. In contrast, an ordinary control group may be administered some standard treatment instead of the experimental one.