Statistics Collaborative - Design and analysis for biomedical research


Randomization schedules

For many years, Statistics Collaborative, Inc. (SCI) has been involved in both the development and validation of randomization schedules. As a developer, we have generated permuted-block (i.e., static) randomization schedules for a variety of study designs, allocation ratios, and sample sizes. We have also prepared many re-supply lists for medications and kits. We are versatile in our development and provide each client with the most appropriate format for the situation at hand. For example, we have prepared electronic randomization and medication lists to upload into interactive voice response (IVR) systems, and we have also produced individual randomization envelopes for remote field trials in sub-Saharan Africa.

We have validated dozens of trials with schemes ranging from dynamic allocations to permuted blocks. We monitor these processes on an ongoing basis and in real time to detect and help correct errors as quickly as possible. We provide thorough documentation to each client at the conclusion of a trial, summarizing the checks performed and the errors detected. Not only do we verify the accuracy of the randomization process, but we also confirm that medication is being re-supplied appropriately and that patients receive the correct study treatment over the course of a trial.

SCI has uncovered several randomization errors over the years. Our careful review has helped prevent larger problems and has reassured clients that the randomization processes of their trials are working smoothly.

Examples of SCI's publications on randomization schedules:

  • Christ-Schmidt H, Downs M. Randomization test using the adaptive urn model design. [Abstract] Controlled Clinical Trials 2002; 23:84S.
  • Downs M, Christ-Schmidt H, Wittes J. A comparison of the urn model to other methods of randomization: an example. Controlled Clinical Trials 2001; 22:92S.
  • Wittes J. Randomized treatment assignment. P Armitage, T Colton (eds). Encyclopedia of Biostatistics. John Wiley, 1998.