Open Access

Use of the score test as a goodness-of-fit measure of the covariance structure in genetic analysis of longitudinal data

Genetics Selection Evolution200335:185

Received: 13 May 2002

Accepted: 7 August 2002

Published: 15 March 2003


Model selection is an essential issue in longitudinal data analysis since many different models have been proposed to fit the covariance structure. The likelihood criterion is commonly used and allows to compare the fit of alternative models. Its value does not reflect, however, the potential improvement that can still be reached in fitting the data unless a reference model with the actual covariance structure is available. The score test approach does not require the knowledge of a reference model, and the score statistic has a meaningful interpretation in itself as a goodness-of-fit measure. The aim of this paper was to show how the score statistic may be separated into the genetic and environmental parts, which is difficult with the likelihood criterion, and how it can be used to check parametric assumptions made on variance and correlation parameters. Selection of models for genetic analysis was applied to a dairy cattle example for milk production.


genetic longitudinal data analysis score test goodness-of-fit measure covariance structure

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Authors’ Affiliations

Institute of Cell Animal and Population Biology, University of Edinburgh
Station de génétique quantitative et appliquée, Institut national de la recherche agronomique
Rothamsted Experimental Station, IACR
Roslin Institute (Edinburgh)


© INRA, EDP Sciences 2003