Document Detail


Properties of the urn randomization in clinical trials.
MedLine Citation:
PMID:  3203525     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
In this article we review the important statistical properties of the urn randomization (design) for assigning patients to treatment groups in a clinical trial. The urn design is the most widely studied member of the family of adaptive biased-coin designs. Such designs are a compromise between designs that yield perfect balance in treatment assignments and complete randomization which eliminates experimental bias. The urn design forces a small-sized trial to be balanced but approaches complete randomization as the size of the trial (n) increases. Thus, the urn design is not as vulnerable to experimental bias as are other restricted randomization procedures. In a clinical trial it may be difficult to postulate that the study subjects constitute a random sample from a well-defined homogeneous population. In this case, a randomization model provides a preferred basis for statistical inference. We describe the large-sample permutational null distributions of linear rank statistics for testing the equality of treatment groups based on the urn design. In general, these permutation tests may be different from those based on the population model, which is equivalent to assuming complete randomization. Poststratified subgroup analyses can also be performed on the basis of the urn design permutational distribution. This provides a basis for analyzing the subset of patients with observed responses when some patients' responses can be assumed to be missing-at-random. For multiple mutually exclusive strata, these tests are correlated. For this case, a combined covariate-adjusted test of treatment effect is described. Finally, we show how to generalize the urn design to a prospectively stratified trial with a fairly large number of strata.
Authors:
L J Wei; J M Lachin
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Controlled clinical trials     Volume:  9     ISSN:  0197-2456     ISO Abbreviation:  Control Clin Trials     Publication Date:  1988 Dec 
Date Detail:
Created Date:  1989-02-03     Completed Date:  1989-02-03     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  8006242     Medline TA:  Control Clin Trials     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  345-64     Citation Subset:  IM    
Affiliation:
Department of Biostatistics, School of Public Health, University of Michigan, Ann Arbor.
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MeSH Terms
Descriptor/Qualifier:
Clinical Trials as Topic / methods*
Humans
Models, Statistical
Prospective Studies
Random Allocation*
Research Design*
Statistics as Topic
Grant Support
ID/Acronym/Agency:
N01-DK-2-2206/DK/NIDDK NIH HHS; R01-AM-35952/AM/NIADDK NIH HHS; R01-CA-45122/CA/NCI NIH HHS
Comments/Corrections
Erratum In:
Controlled Clin Trials 1989 Mar;10(1):following 126

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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