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NCUEIR > College of Science > ma > Periodical Articles > Item 987654321/14451

Please use this identifier to cite or link to this item: http://ir.ncue.edu.tw/ir/handle/987654321/14451

Title:	Inference of Nested Variance Components in a Longitudinal Myopia Intervention Trial
Authors:	Hsiao, Chuhsing Kate;Tsai, Miao-Yu;Chen, Ho-Min
Contributors:	統計資訊研究所
Keywords:	Correlation;Nested repeated measurements;REML;Schwarz criterion
Date:	2005-11
Issue Date:	2012-10-25T09:03:01Z
Publisher:	John Wiley & Sons, Ltd.
Abstract:	This paper was motivated by a double-blind randomized clinical trial of myopia intervention. In addition to the primary goal of comparing treatment e ects, we are concerned with the modelling of correlation that may come from two possible sources, one among the longitudinal observations and the other between measurements taken from both eyes per subject. The data are nested repeated measurements. We suggest three models for analysis. Each one expresses the correlation di erently in various covariance structures. We articulate their di erences and describe the implementations in estimation using commercial statistical software. The computer output can be further utilized to perform model selection with Schwarz criterion. Simulation studies are conducted to evaluate the performance under each model. Data of the myopia intervention trial are reanalysed with these models for illustration. The results indicate that atropine is more e ective in reducing the progression rate, the rates are homogeneous across subjects, and, among the suggested models, the one with independent random e ects of two eyes ts best. We conclude that model selection is a crucial step before making inference with estimates; otherwise the correlation may be attributed incorrectly to a di erent mechanism. The same conclusion applies to other variance components as well.
Relation:	Statistics in Medicine, 24: 3251-3267
Appears in Collections:	[ma] Periodical Articles

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