A Note on the Role of the Propensity Score for Estimating Average Treatment Effects

Hahn [Hahn, J. (1998). On the role of the propensity score in efficient semiparametric estimation of average treatment effects. Econometrica 66:315-331] derived the semiparametric efficiency bounds for estimating the average treatment effect (ATE) and the average treatment effect on the treated (ATET). The variance of ATET depends on whether the propensity score is known or unknown. Hahn attributes this to “dimension reduction.” In this paper, an alternative explanation is given: Knowledge of the propensity score improves upon the estimation of the distribution of the confounding variables.     

试论古汉语中的“鸳鸯”是否是联绵词——兼论联绵词的一种鉴别方式

在现代汉语中“鸳鸯”是联绵词。通过对“鸳鸯”的历时考察，发现“鸳”、“鸯”能单用、分用，有重叠形式，“鸳鸯”有异序词，也和合成词一样。所以用现行的有关联绵词的语素识别方法一双向替换法不好判断它是否是联绵词。通过考察联绵词的来源，提出了新的判断方法，用两个公式区分联绵词与合成词，最终确定“鸳鸯”从古至今都是联绵词。     

英语人称后缀的语义特色

英语中表示人称的后缀很多。由于语源不同,用法差异很大,但又有一定的规律可循。掌握构词特点,了解构词规律,有助于有效地扩充词汇量,加深对词义的了解,促进词汇记忆。探讨了人称后缀的构词特点,归纳了构词规律,分析了语义特征。     

离子晶体外表面束缚极化子

本文计及表面光学声子的作用以及像电荷的作用,采用变分方法对一些材料外表面束缚极化子的基态能量和自陷能作了数值计算,并对结果进行了讨论,发现:对于Ⅰ—Ⅶ、Ⅱ—Ⅵ,Ⅲ—Ⅴ化合物的外表面,均可形成稳定的束缚极化子,且由于表面光学声子的作用,使这一杂质态更加稳定。     

k+l色k-饱和图

给出了一类具有较多边数的k+1色k-饱和图(不含K_k,但添加任一边都含K_k的图)的结构。导出了n点最大k+1色k-饱和图的边数的下界。     

A new approach to statistical efficiency of weighted least squares fitting algorithms for reparameterization of nonlinear regression models

We study nonlinear least-squares problem that can be transformed to linear problem by change of variables. We derive a general formula for the statistically optimal weights and prove that the resulting linear regression gives an optimal estimate (which satisfies an analogue of the Rao-Cramer lower bound) in the limit of small noise.     

Uniformly strong consistency and Berry-Esseen bound of frequency polygons for α-mixing samples

In this article, the frequency polygon investigated by Scott is studied as a nonparametric estimator for α-mixing samples. By some known exponent and moment inequalities, we obtain the uniformly strong consistency and Berry-Esseen bound of the estimator. The present results relax the relevant conditions used by Carbon et al. Furthermore, the convergence rate of the uniformly asymptotic normality is derived, which is O(n^{? 1/11}) under the given conditions.     

An upper bound for the distribution function of a positive definite quadratic form

In this paper the researchers are presenting an upper bound for the distribution function of quadratic forms in normal vector with mean zero and positive definite covariance matrix. They also will show that the new upper bound is more precise than the one introduced by Okamoto [4] and the one introduced by Siddiqui [5]. Theoretical Error bounds for both, the new and Okamoto upper bounds are derived in this paper. For larger number of terms in any given positive definite quadratic form, a rough and easier upper bound is suggested.     

On partial linear additive isotonic regression

In this paper we discuss semiparametric additive isotonic regression models. We discuss the efficiency bound of the model and the least squares estimator under this model. We show that the ordinary least square estimator studied by Huang (2002) and Cheng (2009) for the semiparametric isotonic regression achieves the efficiency bound for the regular estimator when the true parameter belongs to the interior of the parameter space. We also show that the result by Cheng (2009) can be generalized to the case that the covariates are dependent on each other.