Skip to main content

Research Repository

Advanced Search

A systematic review of randomisation method use in RCTs and association of trial design characteristics with method selection

Bruce, Cydney L.; Juszczak, Edmund; Ogollah, Reuben; Partlett, Christopher; Montgomery, Alan


Associate Professor of Medical Statistics and Clinical Trials

Assistant Professor of Medical Statistics and Clinical Trials

Director, nottingham Clinical Trials Unit


Background: When conducting a randomised controlled trial, there exist many different methods to allocate participants, and a vast array of evidence-based opinions on which methods are the most effective at doing this, leading to differing use of these methods. There is also evidence that study characteristics affect the performance of these methods, but it is unknown whether the study design affects researchers’ decision when choosing a method. Methods: We conducted a review of papers published in five journals in 2019 to assess which randomisation methods are most commonly being used, as well as identifying which aspects of study design, if any, are associated with the choice of randomisation method. Randomisation methodology use was compared with a similar review conducted in 2014. Results: The most used randomisation method in this review is block stratification used in 162/330 trials. A combination of simple, randomisation, block randomisation, stratification and minimisation make up 318/330 trials, with only a small number of more novel methods being used, although this number has increased marginally since 2014. More complex methods such as stratification and minimisation seem to be used in larger multicentre studies. Conclusions: Within this review, most methods used can be classified using a combination of simple, block stratification and minimisation, suggesting that there is not much if any increase in the uptake of newer more novel methods. There seems to be a noticeable polarisation of method use, with an increase in the use of simple methods, but an increase in the complexity of more complex methods, with greater numbers of variables included in the analysis, and a greater number of strata.


Bruce, C. L., Juszczak, E., Ogollah, R., Partlett, C., & Montgomery, A. (2022). A systematic review of randomisation method use in RCTs and association of trial design characteristics with method selection. BMC Medical Research Methodology, 22(1), Article 314.

Journal Article Type Article
Acceptance Date Nov 7, 2022
Online Publication Date Dec 7, 2022
Publication Date 2022
Deposit Date Feb 2, 2023
Publicly Available Date Feb 3, 2023
Journal BMC Medical Research Methodology
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 22
Issue 1
Article Number 314
Keywords Research, Randomisation, Stratification, Minimisation, Allocation, Review
Public URL


You might also like

Downloadable Citations