Dependency of the Distribution of Salmonella-Specific Antibodies SP-Ratios on Weight and Sampling Time
American Journal of Theoretical and Applied Statistics
Volume 5, Issue 3, May 2016, Pages: 87-93
Received: Mar. 28, 2016; Accepted: Apr. 14, 2016; Published: Apr. 26, 2016
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Isaac Akpor Adjei, Department of Mathematics, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
Md. Rezaul Karim, Department of Statistics, Jahangirnagar University, Dhaka, Bangladesh
Rachid Muleia, Department of Mathematics and Informatics, Faculty of Science, Eduardo Mondlane University, Maputo, Mozambique
Peter Jouck, FPS Health, Food Chain Safety and Environment, Brussels, Belgium
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Salmonella is one of the major sources of toxin-infection in humans worldwide and is due to transmission of pathogens via pork. This paper aims at investigating the effect of season and animal weight on SP-ratio. Pigs were sampled from different herds and SP-ratios were measured and categorized into two different groups. Depending on the categorization of the response and whether or not clustering is taken into account, different binary logistic and multicategory logit models were considered. Without taking clustering into account, ordinary logistic regression, adjacent logit, continuation-ratio logit and proportional odds model were fitted. GEE and GLMM were considered to correct for the herd-effect. Among the multicategory logit models, the proportional odds model is preferred, since it did not reject the assumption of common slopes. However, regarding the goodness-of-fit test, this model did not adequately fit the data. Both GEE and GLMM have their advantages, depending on the specific focus and question of interest. In all models, the interaction between weight and season was not significant. Weight was found significant, while season was insignificant in all models. As it was expected, weight as indicator for age was found to have a significant effect on SP-ratios.
Salmonella, SP-ratios, Logit Models, GEE, GLMM, Herd-Effect
To cite this article
Isaac Akpor Adjei, Md. Rezaul Karim, Rachid Muleia, Peter Jouck, Dependency of the Distribution of Salmonella-Specific Antibodies SP-Ratios on Weight and Sampling Time, American Journal of Theoretical and Applied Statistics. Vol. 5, No. 3, 2016, pp. 87-93. doi: 10.11648/j.ajtas.20160503.12
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