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ERIC Number: EJ911230
Record Type: Journal
Publication Date: 2010-Dec
Pages: 12
Abstractor: As Provided
Reference Count: 10
ISBN: N/A
ISSN: ISSN-1076-9986
Sample Size for Confidence Interval of Covariate-Adjusted Mean Difference
Liu, Xiaofeng Steven
Journal of Educational and Behavioral Statistics, v35 n6 p714-725 Dec 2010
This article provides a way to determine adequate sample size for the confidence interval of covariate-adjusted mean difference in randomized experiments. The standard error of adjusted mean difference depends on covariate variance and balance, which are two unknown quantities at the stage of planning sample size. If covariate observations are viewed as randomly varying from one study to another, the covariate variance and balance are related to a "t" statistic in the standard error of adjusted mean difference. Using this "t" statistic in the standard error, one can express the expected width of the confidence interval as a function of the sample size. Alternatively, a sample size can be found to achieve a desired probability of having the width of the confidence interval smaller than a predetermined upper bound. (Contains 3 tables.)
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