This is a type of scientific study that is a cornerstone to proper medical research.  Whenever a treatment is to be assessed in a group of patients as to its effectiveness, a similar group of patients must be given no treatment in order to compare the treated group with the control group. Without a control group, no conclusions can really be reached because we do not know how many people in a group of patients will get well spontaneously, for example. There is also the placebo effect of giving a patient a pill, even if it only contains sugar, who subsequently states that they feel better. Controlled studies are made more reliable and more scientific if both the patients and the examiners do not know which group is getting the actual medication and which group is getting the sugar pill. This is referred to as a double-blind controlled study.