Model selection in high-dimensional noisy data: a simulation study

In many practical applications, high-dimensional regression analyses have to take into account measurement error in the covariates. It is thus necessary to extend regularization methods, that can handle the situation where the number of covariates p largely exceed the sample size n, to the case in which covariates are also mismeasured. A variety of methods are available in this context, but many of them rely on knowledge about the measurement error and the structure of its covariance matrix. In this paper, we set the goal to compare some of these methods, focusing on situations relevant for practical applications. In particular, we will evaluate these methods in setups in which the measurement error distribution and dependence structure are not known and have to be estimated from data. Our focus is on variable selection, and the evaluation is based on extensive simulations.     

FDA: strong consistency of the kNN local linear estimation of the functional conditional density and mode

In this paper we present a new estimator of the conditional density and mode when the co-variables are of functional kind. This estimator is a combination of both, the k-Nearest Neighbours procedure and the functional local linear estimation. Then, for each statistical parameter (conditional density or mode), results concerning the strong consistency and rate of convergence of the estimators are presented. Finally, their performances, for finite sample sizes, are illustrated by using simulated data.     

Dynamic inference for non-Markov transition probabilities under random right censoring

The main contribution of this article is the verification of weak convergence of a general non-Markov (NM) state transition probability estimator by Titman, which has not yet been done for any other general NM estimator. A similar theorem is shown for the bootstrap, yielding resampling-based inference methods for statistical functionals. Formulas of the involved covariance functions are presented in detail. Particular applications include the conditional expected length of stay in a specific state, given occupation of another state in the past, and the construction of time-simultaneous confidence bands for the transition probabilities. The expected lengths of stay in a two-sample liver cirrhosis dataset are compared and confidence intervals for their difference are constructed. With borderline significance and in comparison to the placebo group, the treatment group has an elevated expected length of stay in the healthy state given an earlier disease state occupation. In contrast, the Aalen-Johansen (AJ) estimator-based confidence interval, which relies on a Markov assumption, leads to a drastically different conclusion. Also, graphical illustrations of confidence bands for the transition probabilities demonstrate the biasedness of the AJ estimator in this data example. The reliability of these results is assessed in a simulation study.     

An efficient algorithm for finding the M most probable configurationsin probabilistic expert systems

A probabilistic expert system provides a graphical representation of a joint probability distribution which enables local computations of probabilities. Dawid (1992) provided a flow- propagation algorithm for finding the most probable configuration of the joint distribution in such a system. This paper analyses that algorithm in detail, and shows how it can be combined with a clever partitioning scheme to formulate an efficient method for finding the M most probable configurations. The algorithm is a divide and conquer technique, that iteratively identifies the M most probable configurations.     

融资融券交易与市场稳定性:基于动态视角的证据

通过构建“外生信息冲击的门限自回归条件密度(TARCD-X)”模型,进而从动态的视角考察了融资融券实施前后,市场涨跌和交易量增减4种重要的信息冲击对下一期市场稳定性的影响具有怎样的差异,以及融资融券实施后,融资融券余额变动作为新的信息冲击如何影响下一期市场的稳定性.以波动性、暴涨暴跌的不对称性和暴涨暴跌的频繁性3个指标衡量市场的稳定性,研究发现:(1)12种影响关系中,除交易量减小对市场波动性的冲击作用在融资融券实施后有所放大之外,其他11种影响关系均未出现不利变化;(2)融资融券余额的变动没有显著增加市场的波动性和暴涨暴跌的频繁性,但其与暴涨暴跌的不对称性存在显著的相关关系.后者为构建股市暴涨暴跌的预警指标提供了实证依据.     

漫谈“目的复句”

本文从语言实践出发,探讨了语法关系中的目的复句,认为一般语法著作中不提目的复句或作为因果句的一种下属类型是不妥的,目的句有跟因果句不同的句法形式和语义内容,并从目的句的界说及类型,如何区分目的句和因果句,以及目的句的作用三个方面进行了阐述。     

蒙古语族甘青语言的假定式附加成分与突厥语族语言的比较

蒙古语族中土族、东乡、保安、东部裕固等语言的假定式附加成分与同语族的蒙古语相比,显示出较大的差异。但是这些形式却与突厥语族语言表现非常得一致。属于不同语族的数种语言在假定式或条件式上显示出明显、整齐的一致关系,是这些语言早期区域接触的结果蒙古语族;甘...     

Likelihood Factorizations for Mixed Discrete and Continuous Variables

Some general remarks are made about likelihood factorizations, distinguishing parameter-based factorizations and concentration-graph factorizations. Two parametric families of distributions for mixed discrete and continuous variables are discussed. Conditions on graphs are given for the circumstances under which their joint analysis can be split into separate analyses, each involving a reduced set of component variables and parameters. The result shows marked differences between the two families although both involve the same necessary condition on prime graphs. This condition is both necessary and sufficient for simplified estimation in Gaussian and for discrete log linear models.     

条件逻辑及其部分定理的证明与阐释

条件逻辑是以充分条件、必要条件、充分必要条件以及它们之间相互关系为研究对象的逻辑理论。运用现代逻辑的手段,深入研究各种条件联系及其它们相互之间的逻辑关系,这对提高我们的认识能力、有效从事实践具有指导意义。在给出的定义的基础上．我们可以证明有关充分条件、必要条件、充分必要条件的大量定理,条件逻辑就是由定义和定理所构成的形式系统。     

论我国保险人订约说明义务制度的完善

保险合同因保险人和投保人的意思表示一致而成立,并以双方的相互诚信为基础。投保人对保险条款的理解主要依赖保险人提供的说明。目前保险人说明义务履行过程中仍存在许多问题,并且引发了多种保险合同纠纷。其问题主要存在于保险人订约说明时间和说明内容方面。应确立“投保人冷静观察期”制度,区分“法定免责”与“自定免责”条款以及有限制地适用“疑义利益解释规则”,以完善我国保险人订约说明义务制度。