Likelihood-Based Inference for the Shape Parameter of a Two Parameter Weibull Distribution

Based on a Type 2 censored sample, we use the likelihood-based approach to draw likelihood inference on the shape parameter gamma of a two-parameter Weibull distribution. In particular, we derive the profile, conditional and marginal likelihoods of gamma. Numerical results along with some concluding remarks regarding the use of likelihood-based methods for inference are provided.     

新型农村社会养老保险可能面临的主要问题与政策建议

新型农村社会养老保险经过多年的各地积极探索之后,2009年国务院决定在全国开展新型农村社会养老保险试点．这意味着全国统一的新农保制度即将建立。新农保具有鲜明的特征,如强调政府责任、基础养老金的普惠性、个人账户积累等。但同时,新农保在试点过程中也可能遇到一些问题,如如何落实集体补助、如何实现个人账户基金保值增值、如何体现社会统筹等。解决新农保试点中可能遇到的问题,应考虑对相关政策安排作出适当调整。     

叙事的意图说与意图叙事的类型——西方叙事理论中国化的新思考

如何使西方叙事学适合于中国文学研究,是中国文学界在理论上不断探索的问题。新的意图叙事学理论是对西方行为叙事理论的借鉴和修正,它基于叙述学是关于叙述人行为的学说,由于人的行为必有其动机上、意欲上的原因,并从中得到解释,故而叙事学也理应从人的行为动机和意欲入手加以研究的认知。将西方行为叙事所排斥的人物及其心理意图引入叙事学,凸显从人物行为意图的视角研究人的行为叙述及其叙述结构的方法。在此理论方法的观照下,以中国古代小说主人公的行为意图为划分小说类型的标准,从寻找小说主人公、确定主人公主体属性、分析主人公行为意图元类型、主人公意图元内人物关系组合类型等方法、途径,最终划分出中国小说的若干叙事类型,这是对中国小说意图叙事分类方法的一次探索。     

对十七年"歌颂性喜剧"的反思

中国当代喜剧精神失落的原因之一,就是喜剧观念的僵化和迷失,而其突出的表现就是“歌颂性喜剧”被大力提倡。“歌颂性喜剧”在本质上是违背艺术规律和喜剧精神的一个伪命题。被称为“歌颂性喜剧”代表作的喜剧电影《五朵金花》和《今天我休息》则内容虚假、思想肤浅、艺术上做作,这样的作品谈不上是喜剧的成功之作,更不能代表社会主义喜剧的发展方向。因此,“歌颂性喜剧”是一个需要清理和反思的喜剧创作的误区。     

Another view on the analysis of cardiovascular morbidity/mortality trials

In many morbidity/mortality studies, composite endpoints are considered. Although the primary interest is to demonstrate that an invention delays death, the expected death rate is often that low that studies focussing on survival exclusively are not feasible. Components of the composite endpoint are chosen such that their occurrence is predictive for time to death. Therefore, if the time to non-fatal events is censored by death, censoring is no longer independent. As a consequence, the analysis of the components of a composite endpoint cannot be reasonably performed using classical methods for the analysis of survival times like Kaplan-Meier estimates or log-rank tests. In this paper we visualize the impact of disregarding dependent censoring during the analysis and discuss practicable alternatives for the analysis of morbidity/mortality studies. In the context of simulations we provide evidence that copula-based methods have the potential to deliver practically unbiased estimates of hazards of components of a composite endpoint. At the same time, they require minimal assumptions, which is important since not all assumptions are generally verifiable because of censoring. Therefore, there are alternative ways to analyze morbidity/mortality studies more appropriately by accounting for the dependencies among the components of composite endpoints. Despite the limitations mentioned, these alternatives can at minimum serve as sensitivity analyses to check the robustness of the currently used methods.     

An alternative phase II/III design for continuous endpoints

The success rate of drug development has been declined dramatically in recent years and the current paradigm of drug development is no longer functioning. It requires a major undertaking on breakthrough strategies and methodology for designs to minimize sample sizes and to shorten duration of the development. We propose an alternative phase II/III design based on continuous efficacy endpoints, which consists of two stages: a selection stage and a confirmation stage. For the selection stage, a randomized parallel design with several doses with a placebo group is employed for selection of doses. After the best dose is chosen, the patients of the selected dose group and placebo group continue to enter the confirmation stage. New patients will also be recruited and randomized to receive the selected dose or placebo group. The final analysis is performed with the cumulative data of patients from both stages. With the pre‐specified probabilities of rejecting the drug at each stage, sample sizes and critical values for both stages can be determined. As it is a single trial with controlling overall type I and II error rates, the proposed phase II/III adaptive design may not only reduce the sample size but also improve the success rate. An example illustrates the applications of the proposed phase II/III adaptive design. Copyright © 2010 John Wiley & Sons, Ltd.     

人力资本结构刍议

人力资本结构主要是人力资本系统各组成部分之间的比例关系和组织状况。它具有多样性、人口属性、外在性、统一性、动态性、相对稳定性和可调控性特性。从宏观经济角度来看,它主要包括投资主体结构、投资效能结构、人口配置结构、产业配置结构和空间结构,各种结构之间是相互联系的,并表现为不同的功能状态。以人力资本结构的研究为起点,制定切实可行的人力资本投资和管理政策来发挥人力资本优势,将对我国的经济发展产生重要影响。     

Residuals for log-Burr XII regression models in survival analysis

In this paper, we compare three residuals to assess departures from the error assumptions as well as to detect outlying observations in log-Burr XII regression models with censored observations. These residuals can also be used for the log-logistic regression model, which is a special case of the log-Burr XII regression model. For different parameter settings, sample sizes and censoring percentages, various simulation studies are performed and the empirical distribution of each residual is displayed and compared with the standard normal distribution. These studies suggest that the residual analysis usually performed in normal linear regression models can be straightforwardly extended to the modified martingale-type residual in log-Burr XII regression models with censored data.     

Relative risk regression for current status data in case‐cohort studies

We propose using the weighted likelihood method to fit a general relative risk regression model for the current status data with missing data as arise, for example, in case‐cohort studies. The missingness probability is either known or can be reasonably estimated. Asymptotic properties of the weighted likelihood estimators are established. For the case of using estimated weights, we construct a general theorem that guarantees the asymptotic normality of the M‐estimator of a finite dimensional parameter in a class of semiparametric models, where the infinite dimensional parameter is allowed to converge at a slower than parametric rate, and some other parameters in the objective function are estimated a priori. The weighted bootstrap method is employed to estimate the variances. Simulations show that the proposed method works well for finite sample sizes. A motivating example of the case‐cohort study from an HIV vaccine trial is used to demonstrate the proposed method. The Canadian Journal of Statistics 39: 557–577; 2011. © 2011 Statistical Society of Canada     

Non‐parametric Copula Estimation Under Bivariate Censoring

In this paper, we consider non‐parametric copula inference under bivariate censoring. Based on an estimator of the joint cumulative distribution function, we define a discrete and two smooth estimators of the copula. The construction that we propose is valid for a large range of estimators of the distribution function and therefore for a large range of bivariate censoring frameworks. Under some conditions on the tails of the distributions, the weak convergence of the corresponding copula processes is obtained in l^∞([0,1]²). We derive the uniform convergence rates of the copula density estimators deduced from our smooth copula estimators. Investigation of the practical behaviour of these estimators is performed through a simulation study and two real data applications, corresponding to different censoring settings. We use our non‐parametric estimators to define a goodness‐of‐fit procedure for parametric copula models. A new bootstrap scheme is proposed to compute the critical values.