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Article
The Role of Random Allocation in Randomized Controlled Trials: Distinguishing Selection Bias from Baseline Imbalance
Journal of MultiDisciplinary Evaluation
  • Allyn Fives, National University of Ireland, Galway
  • Daniel W. Rusell, Iowa State University
  • Noreen Kearns, National University of Ireland, Galway
  • Rena Lyons, National University of Ireland, Galway
  • Patricia Eaton, National University of Ireland, Galway
  • John Canavan, National University of Ireland, Galway
  • Carmel Devaney, National University of Ireland, Galway
  • Aoife O'Brien, National University of Ireland, Galway
Document Type
Article
Publication Version
Published Version
Publication Date
2-1-2013
Abstract
Background: This paper addresses one threat to the internal validity of a randomized controlled trial (RCT), selection bias. Many authors argue that random allocation is used to ensure baseline equality between study conditions in a given study and that statistically significant differences at pretest mean that randomisation has failed. Purpose: The purpose of this study was to clarify the role of random allocation in an RCT study. Is the role of random allocation to protect against selection bias? And does it have a further role, namely to ensure baseline equality and the absence of statistically significant differences between study conditions at pretest? Setting: The participants for this study were 229 children in 1st and 2nd grade and data were collected as part of an RCT evaluation of a volunteer reading programme piloted in Ireland, Wizards of Words (WoW).
Comments

This is an article from Journal of MultiDisciplinary Evaluation, 2013, 9(20); 33-42. Posted with permission.

Copyright Owner
Journal of MultiDisciplinary Evaluation, Western Michigan University.
Language
en
File Format
application/pdf
Citation Information
Allyn Fives, Daniel W. Rusell, Noreen Kearns, Rena Lyons, et al.. "The Role of Random Allocation in Randomized Controlled Trials: Distinguishing Selection Bias from Baseline Imbalance" Journal of MultiDisciplinary Evaluation Vol. 9 Iss. 20 (2013) p. 33 - 42
Available at: http://works.bepress.com/daniel-russell/17/