In a controlled clinical trial, the patients are placed into groups (see Randomization) called arms, which are compared to one another. The patients in one group all receive the same intervention. Different scenarios develop, depending on the health conditions under study and the aim of the study: each group might receive a different intervention or one group might receive the intervention and the other does not. The researchers evaluate the effects of such interventions on biomedical or health-related outcomes separately in each group and compare the effects among the groups (see Control group).
