-
作者：DAVIDIAN, M
摘要：Estimation of parametric variance functions using transformation of standard deviations based on replication at each design point is common in, but not limited to, assay analysis. It is shown that ignoring unequal replication can lead to bias and inefficiency in estimation. Efficiency comparisons for different transformations for nonormal distributions are given. A method to account for bias is described that can offer robustness to nonnormality and leads to a comparison of Gini''s mean differ...
-
作者：SCHEMPER, M
摘要：Two new measures of the proportion of the variation of possibly censored survival times explained by a given proportional hazards model are presented. It is shown that the previously suggested proportion of explained log likelihood is not a useful measure of predictive precision. The new measures are intuitively appealing and sufficiently simple for routine application.
-
作者：WAKAKI, H
摘要：Asymptotic expansions of the distributions of the linear and the quadratic discriminant functions are derived. The expected misclassification probabilities of these two functions are compared when the covariance matrices are proportional and the sample sizes are equal. Some numerical experiments are carried out to investigate the relation between the parameters and the boundary point such that if the sample size is smaller than the point the linear discriminant function is better than the quad...
-
作者：EBRAHIMI, N; HABIBULLAH, M
作者单位：University of Wisconsin System
摘要：The cumulative distribution function F, of a nonnegative random variable, is said to be new better than used of specified age t0 if .hivin.F (x + t0) .ltoreq. .hivin.F (x) .hivin.F (t0) for all .gtoreq. 0, where .hivin.F = 1 - F. Let A = {F:.hivin.F (x = t0) = .hivin.F (x) .hivin.F (t0), for all x .gtoreq. 0}. We propose a class of test statistics Tk, indexed by a positive integer k, for testing the null hypothesis that F belongs A against the alternative hypothesis that F is new better than u...
-
作者：MARX, BD; SMITH, EP
作者单位：Virginia Polytechnic Institute & State University
-
作者：HEATHCOTE, CR; NICHOLLS, DF
摘要：The contact rate and associated contact number determine the rate of spread of an infectious disease whose population dynamics are described by a mathematical model. It is shown how to obtain least-squares estimates of the contact rate for a standard homogenous univariate model and a four-group model with different contact rates between the groups. The results of a small scale simulation are presented in the case of the four-group model. It is argued that the least-squares method provides gene...
-
作者：THERNEAU, TM; GRAMBSCH, PM; FLEMING, TR
作者单位：University of Washington; University of Washington Seattle
摘要：Graphical methods based on the analysis of residuals are considered for the setting of the highly-used Cox (1972) regression model and for the Andersen-Gill (1982) generalization of that model. We start with a class of martingale-based residuals as proposed by Barlow and Prentice (1988). These residuals and/or their transforms are useful for investigating the functional form of a covariate, the proportional hazards assumption, the leverage of each subject upon the estimates of .beta., and the ...
-
作者：TSAI, WY
摘要：For data subject to random censorship, it is well known that the assumption of independence between censoring time and failure time cannot be tested nonparametrically. For data subject to random truncation, however, it is possible to test independence of truncation time and failure time. A statistic generalizing Kendall''s tau is proposed for testing the independence assumption, and asymptotic properties under the null hypothesis are derived. A conditional permutation test is also derived for ...
