Randomization,balance, and the validity and efficiency of design-adaptive allocation methods |
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Affiliation: | 1. University of Wisconsin, School of Medicine and Public Health, Madison, WI, United States;2. Penn State University, Hershey, PA, United States;3. University of Illinois at Chicago, Chicago, IL, United States;4. Nemours Children''s Health System, Jacksonville, FL, United States;5. Washington University, School of Medicine, St Louis, MO, United States;6. National Jewish Health, Denver, CO, United States;7. Department of Medicine, Brigham and Women''s Hospital, Boston, MA, United States;8. Department of Medicine, University of Arizona, Tucson, AZ, United States;9. Department of Pediatrics, Duke University, Durham, NC, United States;10. University of Michigan, Ann Arbor, MI, United States;11. Wake Forest School of Medicine, Winston-Salem, NC, United States;12. University of Pittsburgh, Pittsburgh, PA, United States;13. University of California San Francisco, San Francisco, CA |
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Abstract: | Few topics have stirred as much discussion and controversy as randomization. A reading of the literature suggests that clinical trialists generally feel randomization is necessary for valid inference, while biostatisticians using model-based inference often appear to prefer nearly optimal designs irrespective of any induced randomness. Dissection of the methods of treatment assignment shows that there are five basic approaches; pure randomizers, true randomizers, quasi-randomizers, permutation testers, and conventional modelers. Four of these have coherent design and analysis strategies, even though they are not mutually consistent, but the fifth and most prevalent approach (quasi-randomization) has little to recommend it. Design-adaptive allocation is defined, it is shown to provide valid inference, and a simulation indicates its efficiency advantage. In small studies, or large studies with many important prognostic covariates or analytic subgroups, design-adaptive allocation is an extremely attractive method of treatment assignment. |
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