Estimating household structure in ancient China by using historical data: a latent class analysis of partially missing patterns

Summary.  Social data often contain missing information. The problem is inevitably severe when analysing historical data. Conventionally, researchers analyse complete records only. Listwise deletion not only reduces the effective sample size but also may result in biased estimation, depending on the missingness mechanism. We analyse household types by using population registers from ancient China (618–907 AD) by comparing a simple classification, a latent class model of the complete data and a latent class model of the complete and partially missing data assuming four types of ignorable and non-ignorable missingness mechanisms. The findings show that either a frequency classification or a latent class analysis using the complete records only yielded biased estimates and incorrect conclusions in the presence of partially missing data of a non-ignorable mechanism. Although simply assuming ignorable or non-ignorable missing data produced consistently similarly higher estimates of the proportion of complex households, a specification of the relationship between the latent variable and the degree of missingness by a row effect uniform association model helped to capture the missingness mechanism better and improved the model fit.     

一种求解双目标线性规划的方法及其在上海市土地使用和交通方面的应用

本文介绍了一种求解双目标线性规划(SBLP)的方法.根据上海市土地使用与交通的现状建立了一个拟动态的模型(BOLT),并用该方法加以求解。根据得到的解对上海市土地使用与交通相互作用的情况进行了分析。     

经济全球化影响下的中国计划生育发展趋势

中国的计划生育是在计划经济体制下形成的,其特点多数与经济全球化的规则有着较大的差距。因此,经济全球化和中国加入世贸组织对中国计划生育的影响是全面而深刻的。在经济全球化的影响下,中国计划生育的发展趋势主要体现在六个方面。     

An individual measure of relative survival

Summary.  Relative survival techniques are used to compare survival experience in a study cohort with that expected if background population rates apply. The techniques are especially useful when cause-specific death information is not accurate or not available as they provide a measure of excess mortality in a group of patients with a certain disease. Whereas these methods are based on group comparisons, we present here a transformation approach which instead gives for each individual an outcome measure relative to the appropriate background population. The new outcome measure is easily interpreted and can be analysed by using standard survival analysis techniques. It provides additional information on relative survival and gives new options in regression analysis. For example, one can estimate the proportion of patients who survived longer than a given percentile of the respective general population or compare survival experience of individuals while accounting for the population differences. The regression models for the new outcome measure are different from existing models, thus providing new possibilities in analysing relative survival data. One distinctive feature of our approach is that we adjust for expected survival before modelling. The paper is motivated by a study into the survival of patients after acute myocardial infarction.     

“每事务于宽厚”的汉章帝

“每事务于宽厚”的汉章帝曹金华汉章帝刘但，是东汉第三代继世令主，也是以＊宽厚长者”著称的封建帝王。在他统治时期，曾一反光武、明帝之“严切”政治，实行了“每事务于宽厚”①的政策。虽然其在位仅十三年，但这一政策却对东汉政权产生了重大而深远的影响。因此颇有...     

用Powell法求颗粒尺寸分布

本文用最优化理论中的Powell直接法求激光粒度仪中的颗粒尺寸分布。数值模拟及对标准颗粒的实测表明,该算法的计算精度高,能较好地解决粒度仪通常存在的计算结果随初始设定值变化的多值性问题。     

中国人口学科国际化水平及其影响因素

国际化是学科成熟与发展的一个重要指标。但是作为世界人口第一大国,中国人口学科的国际化并没有发展到一个相对应的水平。在界定了学科国际化概念的基础上,借助问卷调查数据来分析中国人口学科国际化的现状,探讨中国人口科学继续与国际学界融合所面临的困难及其主要原因。结果表明,中国人口学的国际化明显处于不断萎缩的态势,其直接动因和深层次缘由分别是整个人口学界的国际化意识与能力的减弱,以及人口学科文化与制度本身存在的缺陷。加强国际化的学科文化建设与建立相配套的学科制度是提高中国人口学科国际化水平的重要途径。     

Exact sample size determination in a weibull test plan when there is time censoring

Engineers who conduct reliability tests need to choose the sample size when designing a test plan. The model parameters and quantiles are the typical quantities of interest. The large-sample procedure relies on the property that the distribution of the t -like quantities is close to the standard normal in large samples. In this paper, we use a new procedure based on both simulation and asymptotic theory to determine the sample size for a test plan. Unlike the complete data case, the t -like quantities are not pivotal quantities in general when data are time censored. However we show that the distribution of the t -like quantities only depend on the expected proportion failing and obtain the distributions by simulation for both complete and time censoring case when data follow Weibull distribution. We find that the large-sample procedure usually underestimates the sample size even when it is said to be 200 or more. The sample size given by the proposed procedure insures the requested nominal accuracy and confidence of the estimation when the test plan results in complete or time censored data. Some useful figures displaying the required sample size for the new procedure are also presented.     

A revisit to test the equality of variances of several populations

We revisit the problem of testing homoscedasticity (or, equality of variances) of several normal populations which has applications in many statistical analyses, including design of experiments. The standard text books and widely used statistical packages propose a few popular tests including Bartlett's test, Levene's test and a few adjustments of the latter. Apparently, the popularity of these tests have been based on limited simulation study carried out a few decades ago. The traditional tests, including the classical likelihood ratio test (LRT), are asymptotic in nature, and hence do not perform well for small sample sizes. In this paper we propose a simple parametric bootstrap (PB) modification of the LRT, and compare it against the other popular tests as well as their PB versions in terms of size and power. Our comprehensive simulation study bursts some popularly held myths about the commonly used tests and sheds some new light on this important problem. Though most popular statistical software/packages suggest using Bartlette's test, Levene's test, or modified Levene's test among a few others, our extensive simulation study, carried out under both the normal model as well as several non-normal models clearly shows that a PB version of the modified Levene's test (which does not use the F-distribution cut-off point as its critical value), and Loh's exact test are the “best” performers in terms of overall size as well as power.     

朝鲜族人口自然增长率下降对发展的影响

本文分析了朝鲜族人口减少的主要原因及负面影响,并提出了解决的对策.