Adjusting a Significance Test for Clustering in Designs with Two Levels of Nesting

Autor/in	Hedges, Larry V.
Titel	Adjusting a Significance Test for Clustering in Designs with Two Levels of Nesting
Quelle	In: Journal of Educational and Behavioral Statistics, 34 (2009) 4, S.464-490 (27 Seiten)Infoseite zur Zeitschrift PDF als Volltext Verfügbarkeit
Sprache	englisch
Dokumenttyp	gedruckt; online; Zeitschriftenaufsatz
ISSN	1076-9986
DOI	10.3102/1076998609337251
Schlagwörter	Data Analysis; Statistical Significance; Statistics; Experiments; Educational Research; Research Design; Correlation; Sample Size; Hypothesis Testing; Statistical Analysis + Suchen Sie Ihr Suchwort? Auswertung; Statistik; Erprobung; Bildungsforschung; Pädagogische Forschung; Forschungsdesign; Korrelation; Hypothesenprüfung; Hypothesentest; Statistische Analyse
Abstract	A common mistake in analysis of cluster randomized experiments is to ignore the effect of clustering and analyze the data as if each treatment group were a simple random sample. This typically leads to an overstatement of the precision of results and anticonservative conclusions about precision and statistical significance of treatment effects. This article gives a simple adjustment to the "t" statistic that would be computed if clustering were (incorrectly) ignored in an experiment with two levels of nesting (e.g., classrooms and schools) where treatment assignment is made at the highest (e.g., school) level. The adjustment is a multiplicative factor depending on the number of clusters and subclusters, the cluster and subcluster sample sizes, and the cluster and subcluster intraclass correlations rho[subscript S] and rho[subscript C]. The adjusted "t" statistic has Student's "t" distribution with reduced degrees of freedom. The adjusted statistic reduces to the "t" statistic computed by ignoring clustering when rho[subscript S] = rho[subscript C] = 0. It reduces to the "t" statistic computed using cluster means when rho[subscript S] = 1. rho[subscript S] and rho[subscript C] are between 0 and 1, the adjusted "t" statistic lies between these two and the degrees of freedom are in between those corresponding to these two extremes. (Contains 4 tables.) (As Provided).
Anmerkungen	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
Erfasst von	ERIC (Education Resources Information Center), Washington, DC
Update	2017/4/10