In experimental design, the two main groups are:
Treatment group: This group is exposed to the manipulated independent variable, and the researcher measures the effect of the treatment on the dependent variable.
Control group: This group is not exposed to the manipulated independent variable (the variable being changed or tested). The control group serves as a reference point to compare the results of the experimental group to.
In other words, the control group is used as a baseline to compare with the treatment group, which receives the experimental treatment or intervention.
Two groups in experimental design example
You want to test a new medication to treat headaches. You randomly assign your participants to one of two groups:
The treatment group, who receives the new medication
The control group, who receives a placebo