A comparison between Poisson and zero-inflated Poisson regression models with an application to number of black spots in Corriedale sheep

Abstract

-Dark spots in the fleece area are often associated with dark fibres in wool, which limits its competitiveness with other textile fibres. Field data from a sheep experiment in Uruguay revealed an excess number of zeros for dark spots. We compared the performance of four Poisson and zero-inflated Poisson (ZIP) models under four simulation scenarios. All models performed reasonably well under the same scenario for which the data were simulated. The deviance information criterion favoured a Poisson model with residual, while the ZIP model with a residual gave estimates closer to their true values under all simulation scenarios. Both Poisson and ZIP models with an error term at the regression level performed better than their counterparts without such an error. Field data from Corriedale sheep were analysed with Poisson and ZIP models with residuals. Parameter estimates were similar for both models. Although the posterior distribution of the sire variance was skewed due to a small number of rams in the dataset, the median of this variance suggested a scope for genetic selection. The main environmental factor was the age of the sheep at shearing. In summary, age related processes seem to drive the number of dark spots in this breed of sheep.zero-inflated Poisson / sheep / spot / posterior predictive ability / Bayesian hierarchical model

Delta Boosting Implementation of Negative Binomial Regression in Actuarial Pricing

“…Several studies have shown a considerable improvement in precision by switching from Poisson to the alternative heavier tailed extension like negative binomial, quasi-Poisson, and zero-inflated regression (ZIP) (Ismail and Jemain 2007;Naya et al 2008;Ver Hoef and Boveng 2007). The aforementioned distributions are either compound or mixture of Poisson.…”

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Gene expression analysis identifies new candidate genes associated with the development of black skin spots in Corriedale sheep

“…It is well known that the age of the animals affects spot presence (Naya et al 2008;Peñagaricano et al 2011). Nevertheless, and given the paucity of results in this area, we decided, as a first approximation, to sample across ages to concentrate on identifying those candidate genes that are responsible for the development of black spots under white coats independent of the age of the animal.…”

Network pharmacology of cancer: From understanding of complex interactomes to the design of multi-target specific therapeutics from nature

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