The Application of Overdispersion and Generalized Estimating Equations in Repeated Categorical Data Related To the Sexual Behaviour Traits of Farm Animals

Abstract

In this study, the Poison regression, negative binomial regression and generalized estimating equations were applied to the repeated measurements based on count data obtained from the sexual behaviors of ram lambs. Negative binomial regression was more effective to handle the over dispersion that causes bias in parameter estimations in Poison regression. The generalized estimating equations were used for analyzing repeated categorical data. GEE estimates were obtained by using the exchangeable working correlation. As a result of GEE analyses, it was concluded that flehmen lip curl response, tail raising, mount duration, vocalization and weight of the ram lamb were statistically important (p<0.05) for mount frequent. However, the anogenital sniff found be not significant. © 2007 Asian Network for Scientific Information.