Proportional cause-specific reversed hazards model

The proportional reversed hazards model explains the multiplicative effect of covariates on the baseline reversed hazard rate function of lifetimes. In the present study, we introduce a proportional cause-specific reversed hazards model. The proposed regression model facilitates the analysis of failure time data with multiple causes of failure under left censoring. We estimate the regression parameters using a partial likelihood approach. We provide Breslow's type estimators for the cumulative cause-specific reversed hazard rate functions. Asymptotic properties of the estimators are discussed. Simulation studies are conducted to assess their performance. We illustrate the applicability of the proposed model using a real data set.     

Joint Modeling of Survival and Longitudinal Ordered Data Using a Semiparametric Approach

Medical research frequently focuses on the relationship between quality of life (QoL) and survival time of subjects. QoL may be one of the most important factors that could be used to predict survival, making it worth identifying factors that jointly affect survival and QoL. We propose a semiparametric joint model that consists of item response and survival components, where these two components are linked through latent variables. Several popular ordinal models are considered and compared in the item response component, while the Cox proportional hazards model is used in the survival component. We estimate the baseline hazard function and model parameters simultaneously, through a profile likelihood approach. We illustrate the method using an example from a clinical study.     

“游戏系统”：美国视频游戏内容监管

视频游戏的内容已经引起了社会的关注,而这些关注可能带来法律和政策方面的影响。有问题的内容包括：图形暴力和流血;虚拟的性;部分或全部的裸露镜头;犯罪行为;不适当的模式化观念;种族、民族和宗教的诽谤;毒品、酒精和烟草的使用;赌博;其他挑衅的和不愉快的资料。特别地,人们对儿童的保护问题表示关心。但是,由于美国宪法对涉及视频游戏等言论给予保护,立法机构致力于直接管制含有这种内容游戏的努力一直未能成功。相反地,美国已发展了一系列的非政府机制,这些机制事实上限制这些游戏的发行,并且让购买者能够了解到这些游戏的内容。这种限制措施与有见识的消费者所组成的生态系统依赖于一套非官方的游戏分级制度。这种游戏分级制度依照与游戏开发商签订的合同被强制执行,被游戏经销商和零售商高度重视,以大大减少成人游戏在未满18岁的人群中的销量。如果美国最高法院接受并同意这一当前悬而未决的法律案情的申诉,立法机关将被赋予更大的权力来直接管制这种游戏。     

Quantile regression for competing risks analysis under case-cohort design

The case-cohort design brings cost reduction in large cohort studies. In this paper, we consider a nonlinear quantile regression model for censored competing risks under the case-cohort design. Two different estimation equations are constructed with or without the covariates information of other risks included, respectively. The large sample properties of the estimators are obtained. The asymptotic covariances are estimated by using a fast resampling method, which is useful to consider further inferences. The finite sample performance of the proposed estimators is assessed by simulation studies. Also a real example is used to demonstrate the application of the proposed methods.     

Power and sample size considerations in clinical trials with competing risk endpoints

In clinical trials with a time-to-event endpoint, subjects are often at risk for events other than the one of interest. When the occurrence of one type of event precludes observation of any later events or alters the probably of subsequent events, the situation is one of competing risks. During the planning stage of a clinical trial with competing risks, it is important to take all possible events into account. This paper gives expressions for the power and sample size for competing risks based on a flexible parametric Weibull model. Nonuniform accrual to the study is considered and an allocation ratio other than one may be used. Results are also provided for the case where two or more of the competing risks are of primary interest.     

大型零售商滥用市场优势地位及应对策略

通过分析可以认定大型零售商已经具有市场支配地位,并且滥用其优势地位,导致供应商的利益受到严重侵害,生存状况十分严峻。因此,应当尽快制定和完善相关法律、法规,特别是发挥行业协会的协调、谈判机制,引入公益诉讼制度,在现有法律框架下帮助中小供应商维权。     

A Test for Independence of Competing Risks with Discrete Failure Times

The identifiability problem in Competing Risks is well known. In particular, it implies that independent action or otherwise of the risks cannot be inferred from data alone. However, Crowder (1996) showed that, in the case of purely discrete failure times, an inference can be made. An algebraic criterion was derived which bears essentially on the independence in question. The condition was presented in a theoretical setting but it was pointed out that the quantities involved can be estimated from data and that, therefore, there is the potential to develop practical tests for the hypothesis of independence. It is the purpose of this paper to construct such a test. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dealing with Ties in Failure Time Data

In dealing with ties in failure time data the mechanism by which the data are observed should be considered. If the data are discrete, the process is relatively simple and is determined by what is actually observed. With continuous data, ties are not supposed to occur, but they do because the data are grouped into intervals (even if only rounding intervals). In this case there is actually a non–identifiability problem which can only be resolved by modelling the process. Various reasonable modelling assumptions are investigated in this paper. They lead to better ways of dealing with ties between observed failure times and censoring times of different individuals. The current practice is to assume that the censoring times occur after all the failures with which they are tied.     

Exact inference for competing risks model with generalized type-I hybrid censored exponential data

Recently, exact inference under hybrid censoring scheme has attracted extensive attention in the field of reliability analysis. However, most of the authors neglect the possibility of competing risks model. This paper mainly discusses the exact likelihood inference for the analysis of generalized type-I hybrid censoring data with exponential competing failure model. Based on the maximum likelihood estimates for unknown parameters, we establish the exact conditional distribution of parameters by conditional moment generating function, and then obtain moment properties as well as exact confidence intervals (CIs) for parameters. Furthermore, approximate CIs are constructed by asymptotic distribution and bootstrap method as well. We also compare their performances with exact method through the use of Monte Carlo simulations. And finally, a real data set is analysed to illustrate the validity of all the methods developed here.