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The randomization process involves assigning study participants randomly to experimental or control groups based on their probability of being equally assigned. Randomization is meant to eliminate selection bias and balance known and unknown confounding factors so that the control group is similar to the treatment group as much as possible. A computer program and a random number generator can be used to assign participants to groups in a way that minimizes bias.
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Related Experiment Video

Updated: May 19, 2026

A Vibrotactile Feedback Device for Seated Balance Assessment and Training

A Vibrotactile Feedback Device for Seated Balance Assessment and Training

Published on: January 20, 2019

Allocation techniques for balance at baseline in cluster randomized trials: a methodological review.

Noah M Ivers¹, Ilana J Halperin, Jan Barnsley

¹Family Practice Health Centre, Women's College Hospital, 76 Grenville Street, Toronto, ON, M5S1B2, Canada. noah.ivers@utoronto.ca

|August 3, 2012

Summary

Cluster randomized controlled trials (C-RCTs) often suffer from baseline covariate imbalance. This review guides investigators on selecting restricted randomization methods to improve C-RCT design and credibility.

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Last Updated: May 19, 2026

A Vibrotactile Feedback Device for Seated Balance Assessment and Training

A Vibrotactile Feedback Device for Seated Balance Assessment and Training

Published on: January 20, 2019

Area of Science:

Clinical Trials Methodology
Biostatistics
Epidemiology

Background:

Methodological issues in cluster randomized controlled trials (C-RCTs) are frequently reported.
Existing reviews often focus on intracluster correlation, overlooking baseline covariate imbalance.
Baseline covariate imbalance in C-RCTs can reduce statistical power, precision, and trial credibility.

Purpose of the Study:

To highlight the critical issue of baseline covariate imbalance in C-RCTs.
To review various restricted randomization methods for minimizing covariate imbalance.
To provide guidance for investigators on selecting appropriate allocation techniques for C-RCTs.

Main Methods:

Literature review of restricted randomization techniques.
Analysis of advantages and limitations of stratification, matching, minimization, and covariate-constrained randomization.
Focus on the application and relevance of these methods within the C-RCT context.

Main Results:

Restricted randomization methods can mitigate baseline covariate imbalance in C-RCTs.
Different techniques offer varying benefits and drawbacks for C-RCT design.
Guidance is needed for optimal selection of allocation methods in C-RCTs.

Conclusions:

Addressing baseline covariate imbalance is crucial for robust C-RCTs.
Understanding the nuances of restricted randomization techniques is essential for trialists.
Improved allocation strategies can enhance the validity and reliability of C-RCT findings.