We are interested in evaluate the efficacy of a drug or a procedure in the treatment of a disease, by comparing a new drug with the one currently in use or a placebo.
We assign all the study participants to either the treatment group or the control group. To determine if there are differences in the outcome of interest between the treatment and control groups, we follow participants in these groups over the same time period. Compared to the observational studies, we have direct control over the assignment of participants to either the treatment group or the control group.