Randomized Controlled Trial (RTC)

… a core concept in Quantitative Methods and Atlas104

Concept description

Wikipedia (reference below) defines randomized controlled trial (or randomized control trial, RTC) as “a type of scientific (often medical) experiment which aims to reduce bias when testing a new treatment. The people participating in the trial are randomly allocated to either the group receiving the treatment under investigation or to a group receiving standard treatment (or placebo treatment) as the control.”

Kabisch et al (reference below) write that:

“In clinical research, randomized controlled trials (RCTs) are the best way to study the safety and efficacy of new treatments.

“The quality of an RCT depends on an appropriate study question and study design, the prevention of systematic errors, and the use of proper analytical techniques. All of these aspects must be attended to in the planning, conductance, analysis, and reporting of RCTs. RCTs must also meet ethical and legal requirements.

“In trials with randomized and controlled design (e.g., a two-armed study with parallel groups), the effects of the study treatment (intervention) are compared with those of a control treatment and the patients are randomly assigned to the two groups. The patients in the control group receive either another treatment or a placebo.

“In RCTs the patients are randomly assigned to the different study groups. This is intended to ensure that all potential confounding factors are divided equally among the groups that will later be compared (structural equivalence). These factors are characteristics that may affect the patients’ response to treatment, e.g., weight, age, and sex. Only if the groups are structurally equivalent can any differences in the results be attributed to a treatment effect” rather than the influence of confounders.

Although RCTs are the gold standard with regard to level of evidence, their generalizability, i.e., the extent to which their results can be extrapolated to the wider patient population (external validity) is often questioned, because standardized and controlled study conditions do not adequately reflect clinical reality.”


Wikipedia, Randomized controlled trial, at https://en.wikipedia.org/wiki/Randomized_controlled_trial, accessed 12 May 2018.

Kabisch, Maria et al. “Randomized Controlled Trials: Part 17 of a Series on Evaluation of Scientific Publications.” Deutsches Ärzteblatt International 108.39 (2011): 663–668. at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3196997/, accessed 12 May 2018.

Topic, subject and Atlas course

Research Design (core topic) in Quantitative Methods and Atlas104.

Page created by: Alec Wreford and Ian Clark, last modified 12 May 2018.

Image: Gujarat Bhavnagar, Slideshare.net at https://www.slideshare.net/drnareshchauhan/randomized-controlled-trial, accessed 12 May 2018.