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Stat Med 2014 Aug 30;33(19):3398-404

A note on implementation of decaying product correlation structures for quasi-least squares.

Shults J, Guerra MW


This note implements an unstructured decaying product matrix via the quasi-least squares approach for estimation of the correlation parameters in the framework of generalized estimating equations. The structure we consider is fairly general without requiring the large number of parameters that are involved in a fully unstructured matrix. It is straightforward to show that the quasi-least squares estimators of the correlation parameters yield feasible values for the unstructured decaying product structure. Furthermore, subject to conditions that are easily checked, the quasi-least squares estimators are valid for longitudinal Bernoulli data. We demonstrate implementation of the structure in a longitudinal clinical trial with both a continuous and binary outcome variable.

Category: Journal Article
PubMed ID: #24810946 DOI: 10.1002/sim.6194
Includes FDA Authors from Scientific Area(s): Drugs
Entry Created: 2014-08-24