Editing Randomized controlled trial (section)

==Definition and examples==

An RCT in [[clinical research]] typically compares a proposed new treatment against an existing [[Standard of care#Medical standard of care|standard of care]]; these are then termed the 'experimental' and 'control' treatments, respectively. When no such generally accepted treatment is available, a [[placebo]] may be used in the control group so that participants are [[blinded experiment|blinded]], or not given information, about their treatment allocations. This blinding principle is ideally also extended as much as possible to other parties including researchers, technicians, data analysts, and evaluators. Effective blinding experimentally isolates the physiological effects of treatments from various psychological sources of [[bias]].{{cn|date=November 2023}}

The randomness in the assignment of participants to treatments reduces [[selection bias]] and allocation bias, balancing both known and unknown prognostic factors, in the assignment of treatments.<ref name="Moher-2010">{{Cite journal |vauthors=Moher D, Hopewell S, Schulz KF, Montori V, Gøtzsche PC, Devereaux PJ, Elbourne D, Egger M, Altman DG |date=March 2010 |title=CONSORT 2010 explanation and elaboration: updated guidelines for reporting parallel group randomised trials |journal=BMJ |volume=340 |pages=c869 |doi=10.1136/bmj.c869 |pmc=2844943 |pmid=20332511}}</ref> Blinding reduces other forms of [[Observer-expectancy effect|experimenter and subject biases]].{{cn|date=March 2025}}

A well-blinded RCT is considered the [[Gold standard (test)|gold standard]] for clinical trials. Blinded RCTs are commonly used to test the [[Efficacy#Medicine|efficacy]] of medical [[Health intervention|intervention]]s and may additionally provide information about adverse effects, such as [[adverse drug reactions|drug reactions]]. A randomized controlled trial can provide compelling evidence that the study treatment causes an effect on human health.<ref name="hannan">{{Cite journal |vauthors=Hannan EL |date=June 2008 |title=Randomized clinical trials and observational studies: guidelines for assessing respective strengths and limitations |journal=JACC. Cardiovascular Interventions |volume=1 |issue=3 |pages=211–217 |doi=10.1016/j.jcin.2008.01.008 |pmid=19463302 |doi-access=free}}</ref>

The terms "RCT" and "randomized trial" are sometimes used synonymously, but the latter term omits mention of controls and can therefore describe studies that compare multiple treatment groups with each other in the absence of a control group.<ref name="Ranjith-2005">{{Cite journal |vauthors=Ranjith G |year=2005 |title=Interferon-alpha-induced depression: when a randomized trial is not a randomized controlled trial |journal=Psychotherapy and Psychosomatics |volume=74 |issue=6 |pages=387; author reply 387-387; author reply 388 |doi=10.1159/000087787 |pmid=16244516 |s2cid=143644933}}</ref> Similarly, the [[initialism]] is sometimes expanded as "randomized clinical trial" or "randomized comparative trial", leading to ambiguity in the [[scientific literature]].<ref name="Peto-1976">{{Cite journal |vauthors=Peto R, Pike MC, Armitage P, Breslow NE, Cox DR, Howard SV, Mantel N, McPherson K, Peto J, Smith PG |date=December 1976 |title=Design and analysis of randomized clinical trials requiring prolonged observation of each patient. I. Introduction and design |journal=British Journal of Cancer |volume=34 |issue=6 |pages=585–612 |doi=10.1038/bjc.1976.220 |pmc=2025229 |pmid=795448}}</ref><ref name="Peto-1977">{{Cite journal |vauthors=Peto R, Pike MC, Armitage P, Breslow NE, Cox DR, Howard SV, Mantel N, McPherson K, Peto J, Smith PG |date=January 1977 |title=Design and analysis of randomized clinical trials requiring prolonged observation of each patient. II. analysis and examples |journal=British Journal of Cancer |volume=35 |issue=1 |pages=1–39 |doi=10.1038/bjc.1977.1 |pmc=2025310 |pmid=831755}}</ref> Not all RCTs are randomized ''controlled'' trials (and some of them could never be, as in cases where controls would be impractical or unethical to use). The term randomized controlled clinical trial is an alternative term used in clinical research;<ref name="Wollert-2004">{{Cite journal |vauthors=Wollert KC, Meyer GP, Lotz J, Ringes-Lichtenberg S, Lippolt P, Breidenbach C, Fichtner S, Korte T, Hornig B, Messinger D, Arseniev L, Hertenstein B, Ganser A, Drexler H |year=2004 |title=Intracoronary autologous bone-marrow cell transfer after myocardial infarction: the BOOST randomised controlled clinical trial |journal=Lancet |volume=364 |issue=9429 |pages=141–148 |doi=10.1016/S0140-6736(04)16626-9 |pmid=15246726 |s2cid=24361586}}</ref> however, RCTs are also employed in other research areas, including [[#In social science|many of the social sciences]].