Placebo-Controlled Experiment

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A Placebo-Controlled Experiment is a comparative experiment where the comparator treatment is a placebo treatment (and is given to a placebo-controlled group member).



  • (Wikipedia, 2015) ⇒ Retrieved:2015-6-9.
    • Merely giving a treatment can have nonspecific effects. These are controlled for by the inclusion of patients who receive only a placebo. Subjects are assigned randomly without informing them to which group they belonged. Many trials are doubled-blinded so that researchers do not know to which group a subject is assigned.

      Assigning a subject to a placebo group can pose an ethical problem if it violates his or her right to receive the best available treatment. The Declaration of Helsinki provides guidelines on this issue.


    • QUOTE: A Placebo-controlled study is a way of testing a medical therapy in which, in addition to a group of subjects that receives the treatment to be evaluated, a separate control group receives a sham “placebo” treatment which is specifically designed to have no real effect. Placebos are most commonly used in blinded trials, where subjects do not know whether they are receiving real or placebo treatment. Often, there is also a further "natural history" group that does not receive any treatment at all.

      The purpose of the placebo group is to account for the placebo effect, that is, effects from treatment that do not depend on the treatment itself. Such factors include knowing one is receiving a treatment, attention from health care professionals, and the expectations of a treatment's effectiveness by those running the research study. Without a placebo group to compare against, it is not possible to know whether the treatment itself had any effect.

    • QUOTE: The placebo effect makes it more difficult to evaluate new treatments. Apparent benefits of a new treatment (usually a drug but not necessarily so) may not derive from the treatment but from the placebo effect. This is particularly likely given that new therapies seem to have greater placebo effects.[citation needed] Clinical trials control for this effect by including a group of subjects that receives a sham treatment. The subjects in such trials are blinded as to whether they receive the treatment or a placebo. Often clinical trials are double blinded so that the researchers also do not know which test subjects are receiving the active or placebo treatment.

      The placebo effect in such clinical trials is weaker than in normal therapy since the subjects are not sure whether the treatment they are receiving is active.


  • (Burge et al., 2000) ⇒ P. Sherwood Burge, P. M. A. Calverley, Paul W. Jones, Sally Spencer, Julie A. Anderson, and T. K. Maslen. (2000). “Randomised, double blind, placebo controlled study of fluticasone propionate in patients with moderate to severe chronic obstructive pulmonary disease: the ISOLDE trial." Bmj 320, no. 7245.