Research studies designed to determine the effectiveness of treatment in individuals with a particular disease or condition. The group being studied is known as the target population. The target population is divided into subgroups, one or more of which receives the treatment under study, while the others receive no treatment or the standard treatment. At the end of the study, differences in outcomes between the subgroups can provide a measure of the treatment’s effectiveness. Intervention studies are commonly used to determine the effectiveness of n ew drugs and surgical procedures by comparing the outcomes achieved by the experimental procedure or medication with those achieved by standard treatment or no treatment at all.