http://hdl.handle.net/1957/18467 2013-05-24T04:13:26Z 2013-05-24T04:13:26Z Lin, Hung-Mo Kim, Hae-Young Williamson, John M. Lesser, Virginia M. http://hdl.handle.net/1957/38259 2013-04-18T23:47:28Z 2012-06-01T00:00:00Z

Estimating agreement coefficients from sample survey data Lin, Hung-Mo; Kim, Hae-Young; Williamson, John M.; Lesser, Virginia M. We present a generalized estimating equations approach for estimating the concordance correlation coefficient and the kappa coefficient from sample survey data. The estimates and their accompanying standard error need to correctly account for the sampling design. Weighted measures of the concordance correlation coefficient and the kappa coefficient, along with the variance of these measures accounting for the sampling design, are presented. We use the Taylor series linearization method and the jackknife procedure for estimating the standard errors of the resulting parameter estimates. Body measurement and oral health data from the Third National Health and Nutrition Examination Survey are used to illustrate this methodology. This is the publisher’s final pdf. The published article is copyrighted by Statistics Canada and can be found at: http://www.statcan.gc.ca/ads-annonces/12-001-x/.

2012-06-01T00:00:00Z Olson, Deanna H. Aanensen, David M. Ronnenberg, Kathryn L. Powell, Christopher I. Walker, Susan F. Bielby, Jon Garner, Trenton W. J. Weaver, George The Bd Mapping Group Fisher, Matthew C. http://hdl.handle.net/1957/38032 2013-04-08T17:28:16Z 2013-02-27T00:00:00Z

Mapping the Global Emergence of Batrachochytrium dendrobatidis, the Amphibian Chytrid Fungus Olson, Deanna H.; Aanensen, David M.; Ronnenberg, Kathryn L.; Powell, Christopher I.; Walker, Susan F.; Bielby, Jon; Garner, Trenton W. J.; Weaver, George; The Bd Mapping Group; Fisher, Matthew C. The rapid worldwide emergence of the amphibian pathogen Batrachochytrium dendrobatidis (Bd) is having a profound negative impact on biodiversity. However, global research efforts are fragmented and an overarching synthesis of global infection data is lacking. Here, we provide results from a community tool for the compilation of worldwide Bd presence and report on the analyses of data collated over a four-year period. Using this online database, we analysed: 1) spatial and taxonomic patterns of infection, including amphibian families that appear over-and under-infected; 2) relationships between Bd occurrence and declining amphibian species, including associations among Bd occurrence, species richness, and enigmatic population declines; and 3) patterns of environmental correlates with Bd, including climate metrics for all species combined and three families (Hylidae, Bufonidae, Ranidae) separately, at both a global scale and regional (U. S. A.) scale. These associations provide new insights for downscaled hypothesis testing. The pathogen has been detected in 52 of 82 countries in which sampling was reported, and it has been detected in 516 of 1240 (42%) amphibian species. We show that detected Bd infections are related to amphibian biodiversity and locations experiencing rapid enigmatic declines, supporting the hypothesis that greater complexity of amphibian communities increases the likelihood of emergence of infection and transmission of Bd. Using a global model including all sampled species, the odds of Bd detection decreased with increasing temperature range at a site. Further consideration of temperature range, rather than maximum or minimum temperatures, may provide new insights into Bd-host ecology. Whereas caution is necessary when interpreting such a broad global dataset, the use of our pathogen database is helping to inform studies of the epidemiology of Bd, as well as enabling regional, national, and international prioritization of conservation efforts. We provide recommendations for adaptive management to enhance the database utility and relevance. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Public Library of Science and can be found at: http://www.plos.org/.

2013-02-27T00:00:00Z Van Vuren, Dirk H. Bray, Martin P. Heltzel, Jeannie M. http://hdl.handle.net/1957/37885 2013-03-26T18:06:03Z 2013-02-01T00:00:00Z

Differential investment in twin offspring by female pronghorns (Antilocapra americana) Van Vuren, Dirk H.; Bray, Martin P.; Heltzel, Jeannie M. Differential investment in offspring has been reported for many mammals, often in the context of the Trivers– Willard model of male-biased investment, but evidence of differential investment in pronghorns (Antilocapra americana) is largely lacking. We assessed the causes and consequences of different birth masses of littermate fawns in a pronghorn population in Oregon. The mass differential for co-twins ranged from 0% to 89% (median ¼8.35%). Male-biased investment explained the mass differential in opposite-sex litters but not same-sex litters. The mass differential did not result from mothers producing 1 normal-size fawn and 1 runt fawn, and the smaller fawn was not deficient in physiological condition. Only 29% of fawns survived to 8 weeks and both fawns died in 56% of litters, but co-twin mortalities were largely separate events. Mass did not confer a survival advantage when considering all fawns through age 8 weeks, but there was evidence of such an advantage when comparing fawns within litters before age 18 days. Differential investment in fawns might be a bet-hedging strategy in which the mother accepts a lower expected reproductive success in exchange for a lower variance, but neither the mean nor the variance differed between mothers of different-size (.8.35% mass differential) and similar-size (,8.35%) litters. In fact, there was evidence of increased reproductive success for mothers of different-size litters, much of which stemmed from higher survival 4–6 days after birth. Having different-size fawns reduced the chances of sequential mortality, in which a predator killed one fawn then returned to kill the other. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by American Society of Mammalogists and can be found at: http://www.mammalsociety.org/.

2013-02-01T00:00:00Z O'Donnell, Robert P. (Robert Paul) http://hdl.handle.net/1957/37471 2013-03-14T16:51:37Z 1990-09-27T00:00:00Z

Fisher and logistic discriminant function estimation in the presence of collinearity O'Donnell, Robert P. (Robert Paul) The relative merits of the Fisher linear discriminant function (Efron, 1975) and logistic regression procedure (Press and Wilson, 1978; McLachlan and Byth, 1979), applied to the two group discrimination problem under conditions of multivariate normality and common covariance, have been debated. In related research, DiPillo (1976, 1977, 1979) has argued that a biased Fisher linear discriminant function is preferable when one or more collinearities exist among the classifying variables. This paper proposes a generalized ridge logistic regression (GRL) estimator as a logistic analog to DiPillo's biased alternative estimator. Ridge and Principal Component logistic estimators proposed by Schaefer et al. (1984) for conventional logistic regression are shown to be special cases of this generalized ridge logistic estimator. Two Fisher estimators (Linear Discriminant Function (LDF) and Biased Linear Discriminant Function (BLDF)) and three logistic estimators (Linear Logistic Regression (LLR), Ridge Logistic Regression (RLR) and Principal Component Logistic Regression (PCLR)) are compared in a Monte Carlo simulation under varying conditions of distance between populations, training set s1ze and degree of collinearity. A new approach to the selection of the ridge parameter in the BLDF method is proposed and evaluated. The results of the simulation indicate that two of the biased estimators (BLDF, RLR) produce smaller MSE values and are more stable estimators (smaller standard deviations) than their unbiased counterparts. But the improved performance for MSE does not translate into equivalent improvement in error rates. The expected actual error rates are only marginally smaller for the biased estimators. The results suggest that small training set size, rather than strong collinearity, may produce the greatest classification advantage for the biased estimators. The unbiased estimators (LDF, LLR) produce smaller average apparent error rates. The relative advantage of the Fisher estimators over the logistic estimators is maintained. But, given that the comparison is made under conditions most favorable to the Fisher estimators, the absolute advantage of the Fisher estimators is small. The new ridge parameter selection method for the BLDF estimator performs as well as, but no better than, the method used by DiPillo. The PCLR estimator shows performance comparable to the other estimators when there is a high level of collinearity. However, the estimator gives up a significant degree of performance in conditions where collinearity is not a problem. Graduation date: 1991

1990-09-27T00:00:00Z