The authors show how structural equation modeling can be applied to analyze change in longitudinal multitrait-multimethod (MTMM) studies. For this purpose, an extension of latent difference models (McArdle, 1988; Steyer, Eid, & Schwenkmezger, 1997) to multiple constructs and multiple methods is presented. The model allows investigators to separate true change from measurement error and to analy...

Objective: The main objective of this research was estimation of genetic parameters for five consecutive measurements of egg weights in Isfahan fowl using multi trait model and random regression models. Methods: The statistical models included generation-hatch as a fixed effect, weeks of age as a covariate and additive genetic and individual permanent environmental effects as random effects. Th...

Research examining the structure of multisource performance ratings has demonstrated that ratings are a direct function of both who is doing the rating (rating source) as well as what is being rated (performance dimension). A separate line of research has focused on the extent to which performance ratings are equivalent across sources. To date no research has examined the measurement equivalenc...

The use of genomic selection for changing the growth curve shape of animals, acting simultaneously on the 3 parameters of a Gompertz growth curve, was studied using computer simulation. Results showed that genomic selection modified the growth curve. Responses to all selection criteria were accompanied with a correlated response in mature weight due to the high genetic correlations between matu...