In many clinical trials, one group of patients will be given an experimental treatment, while the "control" group is given either a standard treatment or a "placebo." Researchers are usually looking at how one treatment stacks up against another or even against no treatment at all. To make the comparison useful, the investigator must try both methods on similar groups of subjects. Researchers call the treatment with the predictable, or known effect, the control. The control may be a standard, commonly used treatment, or it may be a placebo. A placebo is an inactive pill, liquid, powder, or other modality with no treatment value (commonly referred to as a "sugar pill"). Some studies use both a standard treatment and a placebo as controls. The control helps an investigator find out if any changes in the experimental group are, in fact, due to the new treatment.