Patients frequently show improvement even when given a sham or "fake" treatment. Such intentionally inert<unk>  treatments can take many forms, such as a pill containing only sugar, a surgery where nothing is actually done, or a medical device (such as ultrasound) that is not actually turned on. Also, due to the body's natural healing ability and statistical effects such as regression to the mean, many patients will get better even when given no treatment at all. Thus, the relevant question when assessing a treatment is not "does the treatment work?" but "does the treatment work better than a<unk>  treatment, or no treatment at all?" As one early clinical trial researcher wrote, "the first object of a therapeutic trial is to discover whether the patients who receive the treatment under investigation are cured more rapidly, more completely or more frequently, than they would have been without it."p.195 More broadly, the aim of a clinical trial is to determine what treatments, delivered in what circumstances, to which patients, in what conditions, are the most effective.
Therefore, the use of<unk> s is a standard control component of most clinical trials which attempt to make some sort of quantitative assessment of the efficacy of medicinal drugs or treatments. Such a test or clinical trial is called a<unk><unk>  study.
Government regulatory agencies approve new drugs only after tests establish not only that patients respond to them, but also that their effect is greater than that of a<unk>  (by way of affecting more patients, by affecting responders more strongly, or both). As a result,<unk>  often are designed in such a way that disadvantages the<unk>  condition".
Placebo-controlled studies
Longitudinal studies
Randomized controlled trial
Longitudinal study
Clinical trial
Cohort study
Evidence-based design
Surrogate endpoint