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Randomized Controlled Trials: Overview and Updates

Controlled Trials

This webpage presents an overview of methods associated with randomized controlled trials. This section has been designed with the intention of providing new and innovative approaches to the conduct of randomized controlled trials as a means of mentoring and supporting health care professionals, academics, students, and research trainees as they engage in this, often times challenging, research methodology.

Mentorship within research is a professional responsibility for all scientists. Dr. Fredericks has chosen to provide mentorship that focuses on randomized controlled trial methodology, as she has received specific training in this area. The use of an online, web-based mentorship approach was selected, as it is perceived as an appropriate tool for disseminating information to a larger international audience. In this way, information can be freely accessed by students, trainees, and academics.

Below are a list articles that addresses issues and/or new approaches to the conduct of randomized controlled trials:

Complex interventions

These interventions typically contain a number of components that can include multiple control and experimental groups, numerous techniques for delivering the intervention, a variety of groups for receiving the intervention and variability in terms of outcomes being assessed.

Complex interventions pose a significant challenge for researcher by way of introduction of error. Below are a few suggested readings that address fundamental issues related to the design and implementation of complex interventions:

1.) Craig, P., Dieppe, P., Macintyre, S., Michie, S., Nazareth, I., & Petticrew, M. (2008). Developing and evaluating complex interventions: the new Medical Research Council guidance. BMJ, 337, a1655. doi:

2.) Movsisyan, A., Melendez-Torres, G. J., & Montgomery, P. (2016). Users identified challenges in applying GRADE to complex interventions and suggested an extension to GRADE. Journal of clinical epidemiology, 70, 191-199.

3.) Wilson, D. T., Walwyn, R. E., Brown, J., Farrin, A. J., & Brown, S. R. (2016). Statistical challenges in assessing potential efficacy of complex interventions in pilot or feasibility studies. Statistical methods in medical research, 25(3), 997-1009.

4.) Gillies, C., Freemantle, N., Grieve, R., Sekhon, J., & Forder, J. (2016). Advancing quantitative methods for the evaluation of complex interventions. Doi: 10.3310/hsdr04160-37

5.) Colantuoni, E., Scharfstein, D. O., Wang, C., Hashem, M. D., Leroux, A., Needham, D. M., & Girard, T. D. (2018). Statistical methods to compare functional outcomes in randomized controlled trials with high mortality. bmj, 360, j5748.

6.) Siebenhofer, A., Paulitsch, M. A., Pregartner, G., Berghold, A., Jeitler, K., Muth, C., & Engler, J. (2018). Cluster-randomized controlled trials evaluating complex interventions in general practices are mostly ineffective: a systematic reviewJournal of clinical epidemiology94, 85-96.


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