A treatment is applied to part of a population and responses are observed. Another part of the population may be used as a control group, in which no treatment is applied. In many cases, subjects in the control group are given a placebo, which is a harmless, unmedicated treatment, that is made to look like the real treatment. The responses of the treatment group and control group can then be compared and studied. For instance, an experiment was performed in which diabetics took cinnamon extract daily while a control group took none. After 40 days, the diabetics who took the cinnamon reduced their risk of heart disease while the control group experienced no change.