Increasing statistical efficiency in RWCTs

Project Summary

This project developed and tested new ways of designing and analyzing clinical trials so that they are more efficient by needing fewer participants and less resources.

Two different methods of increasing efficiency were developed:

  1. The first method improved the way to assign groups of patients to different treatments in cluster-randomized trials. Cluster randomization means that, for example, patients within one hospital will all get the same treatment, while the treatment will vary across different hospitals.
  2. The second method improved the approach used to help doctors summarize the information that is collected from other sources (e.g., from hospital records, other studies and from their experiences with their own patients) about how well the treatment works and then to combine this information with the results from the clinical trial.
    Using the information from other sources can reduce the number of patients needed in the trial to determine which treatment works better.


Ouyang, Y., Xu L., Karim M.E., Gustafson P., Wong H. CRTpowerdist: An R package to calculate attained power and construct the power distribution for cross-sectional stepped-wedge and parallel cluster randomized trials. Computer Methods and Programs in Biomedicine, Vol 208, 2021.

Ouyang, Y. Increasing the efficiency of pragmatic trials using innovative designs and analyses (T). University of British Columbia, 2021.

Ouyang, Y., Karim, M.E., Gustafson, P. et al. Explaining the variation in the attained power of a stepped-wedge trial with unequal cluster sizes. BMC Med Res Methodol 20, 166 (2020).

Wong H., Ouyang Y., Karim M.E. The randomization-induced risk of a trial failing to attain its target power: assessment and mitigation. Trials. 2019 Jun 17;20(1):360.

This project is part of the Real-World Clinical Trials Cluster.


Hubert Wong, PI
Yongdong (Derek) Ouyang
Liang Xu
Ehsan Karim
John Petkau
Paul Gustafson
Thalia Field