title: Reliability of environmental sampling culture results using the negative binomial intraclass correlation coefficient.
abstract: The Intraclass Correlation Coefficient (ICC) is commonly used to estimate the similarity between quantitative measures obtained from different sources. Overdispersed data is traditionally transformed so that linear mixed model (LMM) based ICC can be estimated. A common transformation used is the natural logarithm. The reliability of environmental sampling of fecal slurry on freestall pens has been estimated for Mycobacterium avium subsp. paratuberculosis using the natural logarithm transformed culture results. Recently, the negative binomial ICC was defined based on a generalized linear mixed model for negative binomial distributed data. The current study reports on the negative binomial ICC estimate which includes fixed effects using culture results of environmental samples. Simulations using a wide variety of inputs and negative binomial distribution parameters (r; p) showed better performance of the new negative binomial ICC compared to the ICC based on LMM even when negative binomial data was logarithm, and square root transformed. A second comparison that targeted a wider range of ICC values showed that the mean of estimated ICC closely approximated the true ICC.
authors: Veterinary Medicine Teaching and Research Center, School of Veterinary Medicine, University of California, Davis, 18830 Road 112, Tulare, CA 93274 USA ; Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, One Shields Avenue, Davis, CA 95616 USA.
authors: Sharif S
authors: SS
authors: Aly
authors: Department of Statistics, University of California, Davis, CA 95616 USA.
authors: Jianyang
authors: J
authors: Zhao
authors: Department of Statistics, University of California, Davis, CA 95616 USA.
authors: Ben
authors: B
authors: Li
authors: Department of Statistics, University of California, Davis, CA 95616 USA.
authors: Jiming
authors: J
authors: Jiang
keywords: Generalized linear mixed model; Intraclass correlation coefficient; Negative binomial mixed model; Variance components