Randomized Controlled Trials


Since the first randomized controlled trial (RCT) was published in the BMJ in 1948 about half a million RCTs have been published globally, and it has become the preeminent method in the health sciences for deciding whether a treatment or other health intervention works better than alternative treatments. Its use has spread across all health professions, and it is now common that guidelines in surgery, medicine, primary care, public health, nursing, physiotherapy and many other professions are based on evidence obtained from RCTs, and especially systematic reviews of RCTs. The use of RCTs has spread widely, such as into the field of economic development, where many anti-poverty strategies in low and middle income countries are tested using RCTs.

The reason that RCTs have taken such a front row place in evaluation is simple: this is the only evaluation design which minimizes threats to internal validity (bias) through the design itself. This is because the act of randomization tends to allocate the participants in each arm of the trial so that all arms have a similar distribution of factors that may influence outcome aside from the intervention itself. Some of these factors, such as severity of illness, or age, or other accompanying illnesses are well understood, and could conceivably be balanced even in a non-randomized study. But many factors that influence the outcome of illness are not known, and the astonishing thing about RCTs is that these unknown confounders also tend to be balanced by randomization, and thus their threat to validity of the conclusion tends to be minimized.

Western has a proud history and continuing record of contributing to the development of the RCT design, with many thousands of citations of our seminal papers and foundational book on Cluster Randomization (randomization of groups) and our papers on Pragmatic Trials (RCTs aiming at making a direct inference of the preferred intervention). We are also working on new approaches to integrating cluster randomized trials of policy into the delivery of care and individually randomized RCTs of clinical treatment options into usual health care.


To promote transdisciplinary collaboration on the design and conduct of RCTs, in order to strengthen the method and increase our understanding of how and when to use it; to increase the capacity of researchers to conduct randomized trials and to widen the use of RCT designs at Western, in Canada and globally.


  • Creating a platform that fosters transdisciplinary collaboration in RCT design within our department, and beyond, engaging researchers, service-provider, students and other partners, as well as people with lived experience as participation in RCTs. 

  • Generating epidemiological and biostatistical research that identifies strengths and weaknesses of different design choices in the conduct of RCTs.
  • Developing and test innovative approaches to design and conduct of RCTs.
  • Engaging in teaching, community outreach and knowledge translation initiatives to promote student, clinician, policy maker, community, researcher and funder uptake of RCT designs for evaluation of interventions 
- e.g. promote new designs for RCTs with CIHR to improve their Innovative Clinical Trials (ICT) funding system.

Researchers in the Randomized Trials Cluster: