JRP Submission ID#164
Title: Minimization as an Alternative to Unrestricted Randomization in Educational Research
Category: Provocative Idea
Submitted: Feb 22, 2009
Size: About 3,000 words

** ABSTRACT

This paper describes an alternative to unrestricted randomization in experimental design, termed minimization, which can be used to achieve better balance of critical factors in small to medium-sized experimental studies. Several critical factors are controlled which are known to influence outcomes but which are not the foci of the study. Based on the critical factor values of previously entered participants, a new participant will be allocated into an experimental group to minimize imbalance across groups. Minimization has been primarily employed to date in medical interventions and clinical trials. This article proposes examples of the potential use of minimization in education, its advantages, and limitations.

Keywords: minimization; unstricted randomization; small to medium-sized experimental studies

** EXCERPTS

Randomized experiments have been considered to yield the strongest conclusions regarding the effectiveness of interventions because groups are created that are probabilistically equivalent on all extraneous variables. The most widely used technique is unrestricted randomization, the 'gold standard,' which can make groups probabilistically comparable. . . . However, problems stemming from participant accrual, time, budget, and politics may make conducting simple, unrestricted randomization difficult . . .

Compared to stratified randomization, in which researchers create mutually exclusive subgroups to ensure balance, minimization decreases the total imbalance for all critical variables to achieve better overall balance in a study by balancing multiple participant characteristics simultaneously. . . . Taves (1974) first proposed the minimization technique. . . .

Minimization can be so complex that assignment is difficult to readily compute by hand, thus software packages have been developed. . . . Minimization has been employed primarily in medicine but also in interventions in health psychology. . . .
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DP
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