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Randomizing research participants: Promoting balance and concealment in small samples
Author(s) -
Matthews Ellyn E.,
Cook Paul F.,
Terada Masaka,
Aloia Mark S.
Publication year - 2010
Publication title -
research in nursing and health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 85
eISSN - 1098-240X
pISSN - 0160-6891
DOI - 10.1002/nur.20375
Subject(s) - randomization , confounding , statistics , sample size determination , randomized controlled trial , mathematics , econometrics , sample (material) , restricted randomization , psychology , medicine , surgery , chemistry , chromatography
Randomization is central to rigorous scientific trials. An effective but underutilized approach is urn randomization. To test the ability of urn randomization versus simple randomization to produce balanced groups with small sample sizes, we conducted simulated randomizations: 10 times under sample size scenarios of 20, 40, 60 (group sizes of 10, 20, and 30, respectively), for 30 trials in total. For groups of 20–30, urn surpassed simple randomization in the equal distribution of confounding variables between groups, leading to effects of these variables that were both smaller on average and more consistently close to zero over multiple trials. The urn method is easy to implement and has the advantages of unpredictability of assignment and decreased susceptibility to investigator bias. © 2010 Wiley Periodicals, Inc. Res Nurs Health 33:243–253, 2010