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Randomizing research participants: promoting balance and concealment in small samples
Ellyn E Matthews1, Paul F Cook, Masaka Terada
1College of Nursing, University of Colorado-Denver, 13120 E. 19th Ave., Aurora, CO 80045, USA.
Research in Nursing & Health
|May 26, 2010
Summary
Urn randomization, an underutilized method, better balances groups in small sample size trials compared to simple randomization. This clinical trial method enhances data integrity by minimizing confounding variable effects.
Area of Science:
- Clinical Trials
- Biostatistics
- Research Methodology
Background:
- Randomization is crucial for unbiased scientific studies.
- Simple randomization can lead to group imbalances, especially with small sample sizes.
- Urn randomization offers a potentially more effective alternative.
Purpose of the Study:
- To compare the efficacy of urn randomization versus simple randomization.
- To evaluate group balance and confounding variable distribution in small sample size trials.
- To assess the impact of these randomization methods on study outcomes.
Main Methods:
- Simulated randomizations were conducted for sample sizes of 20, 40, and 60.
- Each sample size scenario was tested 10 times, totaling 30 trials.
- Group balance and the distribution of confounding variables were analyzed.
Main Results:
- Urn randomization demonstrated superior performance in balancing groups for sample sizes of 20-30.
- The urn method resulted in smaller average effects of confounding variables.
- Effects of confounding variables were more consistently close to zero with urn randomization over multiple trials.
Conclusions:
- Urn randomization is an effective and underutilized method for clinical trials.
- It ensures better group balance and reduces bias, particularly in small sample sizes.
- The method is easy to implement, unpredictable, and less susceptible to investigator bias.
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