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ERIC Number: EJ788457
Record Type: Journal
Publication Date: 2008
Pages: 21
Abstractor: Author
Reference Count: 42
ISBN: N/A
ISSN: ISSN-1076-9986
Powerful and Cost-Efficient Designs for Longitudinal Intervention Studies with Two Treatment Groups
Moerbeek, Mirjam
Journal of Educational and Behavioral Statistics, v33 n1 p41-61 2008
Three issues need to be decided in the design stage of a longitudinal intervention study: the number of persons, the number of repeated measurements per person, and the duration of the study. The degree to which polynomial effects vary across persons and the drop-out pattern also influence the statistical power to detect intervention effects. This article presents a framework that allows researchers to calculate the power of a proposed design and compare alternative designs on the basis of their costs and sample sizes. A multilevel regression model with polynomial effects varying across persons is used to relate response to time. The persons' length of stay in the study is modeled using a survival function. (Contains 1 table and 5 figures.)
SAGE Publications. 2455 Teller Road, Thousand Oaks, CA 91320. Tel: 800-818-7243; Tel: 805-499-9774; Fax: 800-583-2665; e-mail: journals@sagepub.com; Web site: http://sagepub.com
Publication Type: Journal Articles; Reports - Descriptive
Education Level: N/A
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A