DOI
https://doi.org/10.25772/NRGN-DK23
Defense Date
2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Biostatistics
First Advisor
Leroy Thacker
Second Advisor
Roy Sabo
Third Advisor
Robert Perera
Fourth Advisor
R. K. Elswick
Fifth Advisor
Patricia Anne Kinser
Abstract
Clinical trials are randomized in part to limit allocation bias, but also to ensure comparability between treatment arms for a baseline variable of concern. Comparable with regard to a baseline variable of concern is necessary for the validity of statistical methods. However, comparability is not guaranteed for trials of any size and is even more likely in trials with < 200 total participants. We propose a new method for adapting the allocation of participants in a sequentially allocated two-armed study with a small sample size to better ensure comparability.
The proposed method calculates the expected final imbalance (lack of comparability) based on the current participant values. Unlike several other methods, our method ensures the final desired sample size for each treatment arm, utilizes the expected final imbalance, increases comparability between treatment arms, can be applied to both categorical and continuous data, and preserves randomization.
When comparing our methods to existing methods of allocation such as the block design, stratification, and minimization, our method either performed better or similarly to existing methods when it came to limiting imbalance.
All of our methods and the existing techniques performed similarly in terms of the average variance of the response, type 1 error, and power. Overall, our method is not difficult to implement and could be added later to a study that utilizes a method that does not balance the groups regarding a baseline variable of concern.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
8-7-2025