Answer:
Ascertain the effectiveness of the treatment
Explanation:
A control group is usually used in experimental. Research usually to establish a higher level of assurance or confidence in one's findings. The control group may be explained as that group in an experiment which do not receive the treatment given to the other group or groups, they may also be called the placebo group. Therefore, adding a control group, the treatment groups (Medicine A and Medicine B) would be weighed against the group which does not receive either of the two medicines.