Abstract
The issue of stratification and its role in patient assignment has generated much discussion, mostly focused on its importance to a study [1,2] or lack thereof [3,4]. This report focuses on a much narrower problem: assuming that stratified assignment is desired, how many factors can be accommodated? This problem is investigated for two methods of balanced patient assignments; the first is based on the minimization method of Taves [5] and the second on the commonly used method of stratified assignment [6,7]. Stimulation results show that the former method can accommodate a large number of factors (10-20) without difficulty but that the latter begins to fail if the total number of distinct combination of factor levels is greater than approximately n/2. The two methods are related to a linear discriminant model, which helps to explain the results.
Original language | English (US) |
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Pages (from-to) | 98-108 |
Number of pages | 11 |
Journal | Controlled Clinical Trials |
Volume | 14 |
Issue number | 2 |
DOIs | |
State | Published - Apr 1993 |
Keywords
- Accidental bias
- adaptive allocation
- clinical trial design
- randomization
- stratification
- treatment imbalance
ASJC Scopus subject areas
- Pharmacology