in this study the data of 2332 lambs from 815 dams and 61 sires, collected during 1993-2004 in kermani sheep breeding station were used to estimate phenotypic, genetic and environmental trends for birth weight (bw), weaning weight (ww), 6 months weight (6mw), 9 months weight (9mw) and yearling weight (yw). heritability estimates were determined for each trait using derivative free reml procedur...

In studies of subjective well-being, economists and other researchers typically use a fixed or random effect estimation to control for unobservable heterogeneity across individuals. Such individual heterogeneity, although substantially reducing the estimated effect of many characteristics, is little understood. This paper shows that personality measures can account for 20% of this heterogeneity...

We discuss the use of fixed and random effects models in the context of educational research and set out the assumptions behind the two modelling approaches. To illustrate the issues that should be considered when choosing between these approaches, we analyse the determinants of pupil achievement in primary school, using data from the Avon Longitudinal Study of Parents and Children. We conclude...

An alternative to the classical mixedmodel with normal random effects is to use a Dirichlet process to model the random effects. Such models have proven useful in practice, and we have observed a noticeable variance reduction, in the estimation of the fixed effects, when the Dirichlet process is used instead of the normal. In this paper we formalize this notion, and give a theoretical justifica...

In this paper I discuss economic processes that may give rise to spatial patterns in data, and explore the relative merits of alternative modeling approaches when data are spatially correlated. Specifically, I present an estimation scheme that allows for spatial random effects, and focus attention on cases in which such a framework may be preferred to the more general fixed effects framework th...

the main objective of this study was to estimate the genetic parameters for multi-trait evaluation of birth weight (bw), gestation length (gl) and calving difficulty (cd) in first-parity iranian holstein dairy cattle. the data included 29,950 calving records collected during 1995 to 2014 by the animal breeding and improvement center of iran. a threshold-linear sire-maternal grandsire model was ...