Final answer:
The group receiving the drink without alcohol is the control group, which is essential in a well-designed experiment for comparing against the treatment effects observed in the experimental group.
Step-by-step explanation:
The group of participants receiving the drink without alcohol added to it comprises the control group. In any well-designed experiment, the control group is essential, as it receives either no treatment or an inactive treatment known as a placebo, which in this case, would be the drink without alcohol. The purpose of having this group is to have a baseline to compare against the experimental group, which receives the actual treatment being tested, which, in this experiment, is the alcohol. This allows researchers to isolate the effects of the alcohol on aggression by comparing it to the control group, establishing whether any observed differences in aggression can be attributed to the alcohol rather than other variables.
Essentially, the experimental group and the control group should be identical in every way except for the exposure to the independent variable, which is the presence of alcohol in this example. This similarity is achieved through random assignment of participants to the two groups. The study design also often includes blinding, where either the participants, the researchers, or both do not know which group participants have been assigned to, which helps prevent any biases or expectations from affecting the results. In most cases, any significant difference in the response variable (which is aggression in this case) between the control group and the experimental group can be ascribed to the influence of the treatment—alcohol.