Researchers set up a study to determine whether large doses of a nutritional supplement would shorten the length of time it takes to recover from a cold. Three thousand volunteers were split into two groups. For two weeks, members of group A took 3,000 mg of the supplement daily. Group B received 3,000 mg of a placebo (sugar pill). At the end of the two-week period, the researchers inserted live cold viruses directly into the noses of all the volunteers. The volunteers in both group A and group B continued to take their daily pills. All the volunteers got colds, and there was no significant difference in the length of time the colds lasted. Which was the experimental group?

Experimental group: In psychological research, the term experimental group is also referred to as the treatment group and is defined as a group that experiences a treatment in a research study or an experiment. An experimental group consists of different test subjects including animals, cells, people, plants, etc and therefore the treatment in the experiment is considered as the variable that the researcher is interested in studying.

In the question above, the experimental group was group A only.