Powerful and Cost-Efficient Designs for Longitudinal Intervention Studies With Two Treatment Groups

Mirjam Moerbeek

Journal of Educational and Behavioral Statistics, 2008, vol. 33, issue 1, 41-61

Abstract: 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.

Keywords: power; sample sizes; study duration; dropout; polynomial growth model (search for similar items in EconPapers)
Date: 2008
References: Add references at CitEc
Citations: View citations in EconPapers (1)

Downloads: (external link)
https://journals.sagepub.com/doi/10.3102/1076998607302630 (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:sae:jedbes:v:33:y:2008:i:1:p:41-61

DOI: 10.3102/1076998607302630

Access Statistics for this article

More articles in Journal of Educational and Behavioral Statistics
Bibliographic data for series maintained by SAGE Publications ().