The Role of Random Allocation in Randomized Controlled Trials: Distinguishing Selection Bias from Baseline Imbalance
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The Department of Human Development and Family Studies focuses on the interactions among individuals, families, and their resources and environments throughout their lifespans. It consists of three majors: Child, Adult, and Family Services (preparing students to work for agencies serving children, youth, adults, and families); Family Finance, Housing, and Policy (preparing students for work as financial counselors, insurance agents, loan-officers, lobbyists, policy experts, etc); and Early Childhood Education (preparing students to teach and work with young children and their families).
History
The Department of Human Development and Family Studies was formed in 1991 from the merger of the Department of Family Environment and the Department of Child Development.
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1991-present
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- College of Human Sciences (parent college)
- Department of Child Development (predecessor)
- Department of Family Environment (predecessor)
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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.