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ERIC Number: EJ782429
Record Type: Journal
Publication Date: 2007
Pages: 25
Abstractor: Author
Reference Count: 38
ISSN: ISSN-0162-3737
Strategies for Improving Precision in Group-Randomized Experiments
Raudenbush, Stephen W.; Martinez, Andres; Spybrook, Jessaca
Educational Evaluation and Policy Analysis, v29 n1 p5-29 2007
Interest has rapidly increased in studies that randomly assign classrooms or schools to interventions. When well implemented, such studies eliminate selection bias, providing strong evidence about the impact of the interventions. However, unless expected impacts are large, the number of units to be randomized needs to be quite large to achieve adequate statistical power, making these studies potentially quite expensive. This article considers when and to what extent matching or covariance adjustment can reduce the number of groups needed to achieve adequate power and when these approaches actually reduce power. The presentation is nontechnical. (Contains 10 figures and 2 notes.)
SAGE Publications. 2455 Teller Road, Thousand Oaks, CA 91320. Tel: 800-818-7243; Tel: 805-499-9774; Fax: 800-583-2665; e-mail:; Web site:
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Elementary Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A