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Design of observational longitudinal...

Basagana, Xavier.

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Design of observational longitudinal studies.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Design of observational longitudinal studies./
Author:	Basagana, Xavier.
Description:	230 p.
Notes:	Adviser: Donna Spiegelman.
Contained By:	Dissertation Abstracts International69-01B.
Subject:	Biology, Biostatistics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3295900
ISBN:	9780549408192

Design of observational longitudinal studies.
Basagana, Xavier.

Design of observational longitudinal studies. - 230 p.

Adviser: Donna Spiegelman.

Thesis (Ph.D.)--Harvard University, 2008.

This dissertation investigates several aspects of study design for longitudinal studies with a continuous outcome and a binary exposure, with special focus on observational studies.

ISBN: 9780549408192Subjects--Topical Terms:

1018416
Biology, Biostatistics.

Design of observational longitudinal studies.
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020 $a 9780549408192
035 $a (UMI)AAI3295900
035 $a AAI3295900
040 $a UMI $c UMI
100 1 $a Basagana, Xavier. $3 1263109
245 1 0 $a Design of observational longitudinal studies.
300 $a 230 p.
500 $a Adviser: Donna Spiegelman.
500 $a Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0033.
502 $a Thesis (Ph.D.)--Harvard University, 2008.
520 $a This dissertation investigates several aspects of study design for longitudinal studies with a continuous outcome and a binary exposure, with special focus on observational studies.
520 $a User-friendly software, which handles all scenarios described above, is publicly available at http://www.hsph.harvard.edu/faculty/spiegelman/optitxs.html.
520 $a Chapter 1 focuses on studies where the exposure is time-invariant. It covers a wide range of topics in study design. Formulas for power, sample size, number of repeated measurements, and the optimal combination of number of participants and number of repeated measures which maximize power for a given budget, or which minimize the total cost of the study while achieving a specific power are derived. The effect of all parameters on these quantities is studied. Some of the difficulties investigators need to address when the study is not randomized are discussed.
520 $a Chapter 2 provides design formulas for studies where interest is in the main effect of a time-varying exposure. In observational studies, several exposure patterns are observed, they are often severely imbalanced, and the design matrix is unknown a priori. The prevalence and the intraclass correlation of exposure, which is a measure of within-subject variation in exposure, are additional parameters needed to compute study design quantities when the response has compound symmetry covariance. For other covariance structures, these parameters allow the computation of reasonable approximations. It is shown that, in most situations, having a time-varying instead of a time-invariant exposure produces gains in efficiency, which can be substantial in studies with several repeated measurements.
520 $a Chapter 3 provides study design formulas for studies that compare rates of change as a function of a time-varying exposure. Formulas are derived for models that assume an acute or a cumulative effect of exposure, and for models that do and do not separate the within- and between-subject effects. Exact formulas as a function of the exposure prevalence and intraclass correlation can be derived for a few simple cases, while for the others reasonable approximations are obtained. For the cumulative effect model, efficiency is lost in most cases when having a time-varying exposure, while for the acute effect model both gains and losses in efficiency are observed.
590 $a School code: 0084.
650 4 $a Biology, Biostatistics. $3 1018416
690 $a 0308
710 2 $a Harvard University. $3 528741
773 0 $t Dissertation Abstracts International $g 69-01B.
790 $a 0084
790 1 0 $a Spiegelman, Donna, $e advisor
791 $a Ph.D.
792 $a 2008
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3295900