There are three primary types of control groups: 1) historical controls, 2) placebo/sham
controls and 3) active controls. The selection of a control group depends on the research
question of interest. If it is desirable to show any effect, then placebo-controls are the most
credible and should be considered as a first option. However placebo controls may not be
ethical in some cases and thus active controls may be utilized. If it is desirable to show
noninferiority or superiority to other active interventions then active controls may be
utilized