Randomizing research participants: Promoting balance and concealment in small samples†
Article first published online: 1 APR 2010
Copyright © 2010 Wiley Periodicals, Inc.
Research in Nursing & Health
Volume 33, Issue 3, pages 243–253, June 2010
How to Cite
Matthews, E. E., Cook, P. F., Terada, M. and Aloia, M. S. (2010), Randomizing research participants: Promoting balance and concealment in small samples. Res. Nurs. Health, 33: 243–253. doi: 10.1002/nur.20375
This research was supported by NIH/NINR grant #NR04817 (PI: Sousa), NIH/NINR grant #NR010587 (PI: Matthews), and by the Biostatistics, Epidemiology, and Research Design Core of the Colorado Clinical and Translational Research Institute (NIH grant #1UL1RR025780-01).
- Issue published online: 17 MAY 2010
- Article first published online: 1 APR 2010
- Manuscript Accepted: 15 FEB 2010
- randomized controlled trial;
- adaptive randomization;
- allocation concealment;
- treatment allocation
Randomization is central to rigorous scientific trials. An effective but underutilized approach is urn randomization. To test the ability of urn randomization versus simple randomization to produce balanced groups with small sample sizes, we conducted simulated randomizations: 10 times under sample size scenarios of 20, 40, 60 (group sizes of 10, 20, and 30, respectively), for 30 trials in total. For groups of 20–30, urn surpassed simple randomization in the equal distribution of confounding variables between groups, leading to effects of these variables that were both smaller on average and more consistently close to zero over multiple trials. The urn method is easy to implement and has the advantages of unpredictability of assignment and decreased susceptibility to investigator bias. © 2010 Wiley Periodicals, Inc. Res Nurs Health 33:243–253, 2010