Marginal Regression of Gaps Between Recurrent Events

Recurrent event data typically exhibit the phenomenon of intra-individual correlation, owing to not only observed covariates but also random effects. In many applications, the population may be reasonably postulated as a heterogeneous mixture of individual renewal processes, and the inference of interest is the effect of individual-level covariates. In this article, we suggest and investigate a marginal proportional hazards model for gaps between recurrent events. A connection is established between observed gap times and clustered survival data with informative cluster size. We subsequently construct a novel and general inference procedure for the latter, based on a functional formulation of standard Cox regression. Large-sample theory is established for the proposed estimators. Numerical studies demonstrate that the procedure performs well with practical sample sizes. Application to the well-known bladder tumor data is given as an illustration.     

Expressing Estimators of Expected Quality Adjusted Survival as Functions of Nelson-Aalen Estimators

Quality adjusted survival has been increasingly advocated in clinical trials to be assessed as a synthesis of survival and quality of life. We investigate nonparametric estimation of its expectation for a general multistate process with incomplete follow-up data. Upon establishing a representation of expected quality adjusted survival through marginal distributions of a set of defined events, we propose two estimators for expected quality adjusted survival. Expressed as functions of Nelson-Aalen estimators, the two estimators are strongly consistent and asymptotically normal. We derive their asymptotic variances and propose sample-based variance estimates, along with evaluation of asymptotic relative efficiency. Monte Carlo studies show that these estimation procedures perform well for practical sample sizes. We illustrate the methods using data from a national, multicenter AIDS clinical trial.     

试论海权的历史发展规律

海权在本质上是一国控制和利用海洋的能力和影响力。海权的发展包括一国建立和运用海权的全过程。海权的建立和运用有其自身的特点和规律，探寻这些规律，对于深化海权思想，吸收和借鉴海权发展过程中的经验教训，指导现实的海权发展，具有重要的理论意义。     

A Simple Corrected Score for Logistic Regression with Errors-in-Covariates

We develop a simple corrected score for logistic regression with errors-in-covariates. The new method is an extension of the consistent functional methods proposed by Huang and Wang (2001) and is closely related to the corrected score method by Nakamura (1990 Nakamura, T. (1990). Corrected score function for errors-in-variables models: Methodology and application to generalized linear models. Biometrika. 77:127–137.[Crossref], [Web of Science ®] , [Google Scholar]) and Stefanski (1989 Stefanski, L.A. (1989). Unbiased estimation of a nonlinear function a normal mean with application to measurement error models. Commun. Stat. Ser. A - Theory Methods. 18:4335–4358.[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). The new method requires that the measurement error distribution is known, but does not require normality. The new method yields a consistent and asymptotically normal estimator under regularity conditions. We examine the finite-sample performance of the new estimator through simulation studies. Finally, we illustrate the new method by applying it to an AIDS study.     

Censored regression with the multistate accelerated sojourn times model

Many disease processes are characterized by two or more successive health states, and it is often of interest and importance to assess state-specific covariate effects. However, with incomplete follow-up data such inference has not been satisfactorily addressed in the literature. We model the logarithm-transformed sojourn time in each state as linearly related to the covariates; however, neither the distributional form of the error term nor the dependence structure of the states needs to be specified. We propose a regression procedure to accommodate incomplete follow-up data. Asymptotic theory is presented, along with some tools for goodness-of-fit diagnostics. Simulation studies show that the proposal is reliable for practical use. We illustrate it by application to a cancer clinical trial.     

公共图书馆实行总分馆制管理模式研究

总分馆制是公共图书馆发展的基本方向.近几年来,国内不少公共图书馆结合自身的实际,在总分馆建设方面作了有益的探索,涌现了"厦门模式"、"苏州模式"、"嘉兴模式"、"佛山模式"等众多形式多样的总分馆制管理模式.本文在阐述总分馆制基本特征、分析相关模式的基础上,对公共图书馆如何实行总分馆制作了理性思考,提出了相应对策措施.     

Further studies on the scale estimation in the censored two sample accelerated life model

Yang (1998) proposes a new class of scale estimators for the censored two sample accelerated life model. Unlike most previous results, Yang's estimators have the property that their asymptotic variance can be easily and reliably estimated, and the inferences on the scale parameter can be easily obtained. In this article, we further study the estimation function of Yang. Several new classes of weights and a new slope estimate are considered. Throughout extensive numerical studies, it was found that a new weight together with the use of the new slope results in an estimating function that improved the choices recommended by Yang.     

Test-Based Interval Estimation Under the Accelerated Failure Time Model

Some new results of a distance—based (DB) model for prediction with mixed variables are presented and discussed. This model can be thought of as a linear model where predictor variables for a response Y are obtained from the observed ones via classic multidimensional scaling. A coefficient is introduced in order to choose the most predictive dimensions, providing a solution to the problem of small variances and a very large number n of observations (the dimensionality increases as n). The problem of missing data is explored and a DB solution is proposed. It is shown that this approach can be regarded as a kind of ridge regression when the usual Euclidean distance is used.     

基于顾客渠道偏好的服务竞争模型

由传统零售渠道和在线直销渠道组成的双渠道供应链中,两种渠道带给顾客不同的购物服务体验,能更好地满足不同渠道偏好的顾客需要,但两种渠道之间又存在竞争关系。针对两种渠道带给顾客的服务体验的差异性,构建考虑顾客渠道偏好的双渠道供应链服务竞争模型,研究制造商的最优渠道选择策略以及在线渠道的增加给传统单渠道供应链和顾客带来的影响。研究结果表明,能否扩大市场需求是判断制造商是否选择双渠道策略的充分条件,但是增加在线渠道之后,供应链存在服务歧视现象,可能造成市场需求减少;在线渠道的增加始终损害零售商的利益,并且可能导致供应链整体收益减少和顾客整体效用水平下降,最终导致社会福利的损失。借助数值分析发现,如果存在大量未开拓的潜在市场需求,顾客对在线渠道偏好程度的提高将有助于提升供应链整体收益和顾客整体效用水平,反之亦然。     

Fast Censored Linear Regression

Weighted log‐rank estimating function has become a standard estimation method for the censored linear regression model, or the accelerated failure time model. Well established statistically, the estimator defined as a consistent root has, however, rather poor computational properties because the estimating function is neither continuous nor, in general, monotone. We propose a computationally efficient estimator through an asymptotics‐guided Newton algorithm, in which censored quantile regression methods are tailored to yield an initial consistent estimate and a consistent derivative estimate of the limiting estimating function. We also develop fast interval estimation with a new proposal for sandwich variance estimation. The proposed estimator is asymptotically equivalent to the consistent root estimator and barely distinguishable in samples of practical size. However, computation time is typically reduced by two to three orders of magnitude for point estimation alone. Illustrations with clinical applications are provided.