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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/398

Title: Two latent variable risk assessment approaches for combined continuous and discrete outcomes from developmental toxicity data
Authors: Geys, Helena
Regan, Meredith M.
Catalano, Paul J.
Molenberghs, Geert
Keywords: Categorical data
Longitudinal data
Clustered data
Issue Date: 2001
Citation: Journal of Agricultural Biological and Environmental Statistics, 6(3). p. 340-355
Abstract: Measurements of both continuous and discrete outcomes are encountered in many statistical problems. Here we consider the particular context of teratology studies, where quantitative risk assessment is aimed at determining the effect of dose on the probability that an individual fetus is malformed or of low birth weight, both being important measures of teratogenicity. We will introduce two different joint marginal mean models for outcomes of a mixed nature. First, we propose the Plackett-Dale approach, where for each binary outcome it is assumed that there exists an underlying latent variable. The latent malformation outcomes are then assumed to follow a Plackett distribution. The second approach we consider is a probit approach. Here it is assumed that there exists an underlying continuous variable for each binary outcome, so the joint distribution for weight and malformation can be assumed to follow a multivariate normal distribution. In both cases, specification of the full distribution will be avoided using pseudolikelihood and generalized estimating equations methodology, respectively. Quantitative risk assessment is illustrated using data from two developmental toxicology experiments.
URI: http://hdl.handle.net/1942/398
DOI: 10.1198/108571101317096550
ISI #: 000172409200003
ISSN: 1085-7117
Category: A1
Type: Journal Contribution
Validation: ecoom, 2002
Appears in Collections: Research publications

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