page_title: Randomized controlled trial
hierarchical_section_title: Randomized controlled trial
caption_attribution_description: English: This flowchart is based on "Flow diagram of the progress through the phases of a parallel randomised trial of two groups (that is, enrolment, intervention allocation, follow-up, and data analysis)" (http://www.bmj.com/content/vol340/issuemar23_1/images/large/schk712109.f1_default.jpeg), which is part of: Schulz KF, Altman DG, Moher D; for the CONSORT Group. CONSORT 2010 Statement: updated guidelines for reporting parallel group randomised trials. BMJ. 2010 Mar 23;340:c332. doi: 10.1136/bmj.c332. (http://www.bmj.com/cgi/content/full/340/mar23_1/c332) The original diagram has been redrawn and modified to: (1) use American English spelling ("enrollment," "randomized," "analyzed"); (2) reduce the amount of text (e.g., deleted all occurrences of "(n=...)" and "(give reasons)", deleted specific exclusion reasons); (3) un-bold sideways text near left margin; (4) put steps in logical/chronological order (e.g., reversed order of "lost to follow-up" and "discontinued intervention" as latter could occur without former); (5) increase the size of downward-pointing arrows relative to text; (6) from top to bottom, progressively decrease the font size of text in boxes connected by downward-pointing arrows, to suggest decrease in number of subjects between "assessed for eligibility" and "analyzed."
context_page_description: A randomized controlled trial is a type of scientific experiment that aims to reduce certain sources of bias when testing the effectiveness of new treatments; this is accomplished by randomly allocating subjects to two or more groups, treating them differently, and then comparing them with respect to a measured response. One group—the experimental group—receives the intervention being assessed, while the other—usually called the control group—receives an alternative treatment, such as a placebo or no intervention. The groups are monitored under conditions of the trial design to determine the effectiveness of the experimental intervention, and efficacy is assessed in comparison to the control. There may be more than one treatment group or more than one control group.
  The trial may be blinded, meaning that information which may influence the participants is withheld until after the experiment is complete. A blind can be imposed on any participant of an experiment, including subjects, researchers, technicians, data analysts, and evaluators. Effective blinding may reduce or eliminate some sources of experimental bias.
context_section_description: A randomized controlled trial (or randomized control trial; RCT) is a type of scientific (often medical) experiment that aims to reduce certain sources of bias when testing the effectiveness of new treatments; this is accomplished by randomly allocating subjects to two or more groups, treating them differently, and then comparing them with respect to a measured response. One group—the experimental group—receives the intervention being assessed, while the other—usually called the control group—receives an alternative treatment, such as a placebo or no intervention. The groups are monitored under conditions of the trial design to determine the effectiveness of the experimental intervention, and efficacy is assessed in comparison to the control.  There may be more than one treatment group or more than one control group.
  The trial may be blinded, meaning that information which may influence the participants is withheld until after the experiment is complete. A blind can be imposed on any participant of an experiment, including subjects, researchers, technicians, data analysts, and evaluators. Effective blinding may reduce or eliminate some sources of experimental bias.
  The randomness in the assignment of subjects to groups reduces selection bias and allocation bias, balancing both known and unknown prognostic factors, in the assignment of treatments. Blinding reduces other forms of experimenter and subject biases.
  A well-blinded RCT is often considered the gold standard for clinical trials. Blinded RCTs are commonly used to test the efficacy of medical interventions and may additionally provide information about adverse effects, such as drug reactions.
  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. Similarly, the initialism is sometimes expanded as "randomized clinical trial" or "randomized comparative trial", leading to ambiguity in the scientific literature. Not all randomized clinical trials are randomized controlled trials (and some of them could never be, as in cases where controls would be impractical or unethical to institute). The term randomized controlled clinical trial is an alternative term used in clinical research; however, RCTs are also employed in other research areas, including many of the social sciences.
caption: Flowchart of four phases (enrollment, allocation, intervention, follow-up, and data analysis) of a parallel randomized trial of two groups (in a controlled trial, one of the interventions serves as the control), modified from the CONSORT (Consolidated Standards of Reporting Trials) 2010 Statement[1]
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