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Full-Text Articles in Physical Sciences and Mathematics
On Testing For Significant Quantitative Trait Loci (Qtl) Effects When Variances Are Unequal, Pradeep Singh, Shesh N. Rai
On Testing For Significant Quantitative Trait Loci (Qtl) Effects When Variances Are Unequal, Pradeep Singh, Shesh N. Rai
Conference on Applied Statistics in Agriculture
The basic theory of QTL (Quantitative Trait Loci) mapping is to score a population for a quantitative trait according to the marker genotype, and then to use statistics to identify differences associated with the markers and the quantitative trait of interest. Permutation based methods have been used to estimate threshold values for quantitative mapping. The permutation test based on the Student t-test for equality of means does not control Type I error rate to its nominal value when variances are unequal. In this study we propose a modification of the Student t-test based on the jackknife estimator of population variance. …
Sample Size Determination In Animal Health Studies, Zhanglin Cui, Alan G. Zimmermann, Daniel H. Mowrey
Sample Size Determination In Animal Health Studies, Zhanglin Cui, Alan G. Zimmermann, Daniel H. Mowrey
Conference on Applied Statistics in Agriculture
Oftentimes in animal health studies, a treatment group is randomly assigned to a pen of animals, and the pen of animals as a whole is treated (fed the same medicated feed or water) together. In this scenario, the pen of animals is the experimental unit and the individual animal may be an observational unit. In addition to having the pen as the experimental unit, if multiple sites are used and site is treated as a random factor, this adds complexity to the study. To properly design the study, it is necessary to determine the number of animals in a pen, …
Small Sample Power Characteristics Of Generalized Mixed Model Procedures For Binary Repeated Measures Data Using Sas, Matthew Beckman, Walter W. Stroup
Small Sample Power Characteristics Of Generalized Mixed Model Procedures For Binary Repeated Measures Data Using Sas, Matthew Beckman, Walter W. Stroup
Conference on Applied Statistics in Agriculture
Researchers in the agricultural and biological sciences often conduct experiments with repeated measures and categorical response variables. Recent advances in statisticalcomputing have made several options available to analyze data from these experiments. For example, SAS has several procedures based on generalized mixed model theory. These include PROC GENMOD, MIXED, NLMIXED, and the GLIMMIX macro. Inference for these procedures depends on asymptotic theory. While statistics literature contains some information about the small-sample behavior, there is much that remains unknown. This presentation will focus on Bernoulli response variables. Power characteristics are compared via simulation for several scenarios involving relatively small repeated measures …
Empirical Estimates Of Power For Binomial Data With Mixed Models, R. K. Splan, L. D. Van Vleck, H. D. Hafs
Empirical Estimates Of Power For Binomial Data With Mixed Models, R. K. Splan, L. D. Van Vleck, H. D. Hafs
Conference on Applied Statistics in Agriculture
Observations on return to estrus from anestrus postpartum beef cows were used as the basis for a simulation study to develop a method to determine numbers of locations and animals per treatment per location to achieve a specified power of test. Estimates of among location and total variance were obtained by REML from the data set and then used to generate simulated data for the binomial trait. Each combination of several pre-determined factors was replicated 1000 times. Pre-determined factors were number of locations, number of animals per treatment per location, desired detectable difference due to treatment, alpha-probability level and ratio …