Approximate inference in multivariate nonlinear functional relationships

An estimation procedure based on estimating equations is presented for the parameters in a multivariate functional relationship model, where all observations are subject to error. The covariance matrix of the observational errors may be parametrized and is allowed to be different for different sets of observations. Estimators are defined for the unknown relation parameters and error parameters.
For linear models (i.e. where the model function is linear in the incidental parameters) the estimators are consistent and asymptotically normal. A consistent expression for the covariance matrix of the estimators is derived. The results are valid for general error distributions.
For nonlinear models the estimators are based on locally linear approximations to the model function. The afore mentioned properties of the estimators are now only approximately valid. The adequacy of the approximate inference, based on asymptotic theory for the linearized model, needs at least informal check. Some examples are given to illustrate the estimation procedure.     

网络编程文件的上传漏洞以及解决方法

互联网的应用日益复杂,客服需求也越来越多样化,个性化,从而使得客户端的功能也更随着变化,最显著的就是要能提供上传功能,本文通过实例来阐述文件上传原理以及文件上传时的漏洞,漏洞的类型原理等等。     

Recovered errors and normal diagnostics in regression

Diagnostics for normal errors in regression typically utilize ordinary residuals, despite the failure of assumptions to validate their use. Case studies here show that such misuse may be critical. A remedy invokes recovered errors having the required properties, taking into account that such errors are closer to normality than are disturbances in the observations themselves. Simulation studies show consistent improvement over the usual methods in small samples. In addition, effects on normal diagnostics due to various model violations are examined. Received: January 1999     

Time-series–cross-section Data

This article treats the analysis of 'time-series–cross-section' (TSCS) data. Such data consists of repeated observations on a series of fixed units. Examples of such data are annual observations on the political economy of OECD nations in the post-war era. TSCS data is distinguished from 'panel' data, in that asymptotics are in the number of repeated observations, not the number of units.
The article begins by treating the complications of TSCS data in an 'old-fashioned' manner, that is, as a nuisance which causes estimation difficulties. It claims that TSCS data should be analyzed via ordinary least squares with 'panel correct standard errors' rather than generalized least squares methods. Dynamics should be modeled via a lagged dependent variable or, if appropriate, a single equation error correction model.
The article then treats more modern issues, in particular, the modeling of spatial effects and heterogeneity. It also claims that heterogeneity should be assessed with 'panel cross-validation' as well as more standard tests. The article concludes with a discussion of estimation in the presence of a binary dependent variable.     

Nonresponse and Recall Errors in a Study of Absence because of Illness: An Analysis of Their Effects on Distributions and Relationships

Using administrative data as validating standard, we studied the combined effects of two sources of survey error – nonresponse and recall errors – on distributional and substantive bias in a mail survey of absence because of illness among the employees of a Dutch road building company (response rate 77%). No distributional bias was found in five socio-demographic variables (sex, age, years of service, function, and district), but both nonresponse bias and recall bias occurred in our central dependent variables: frequency and duration of absence because of illness. Nonrespondents were on sick leave more frequently and longer than respondents. Furthermore, the self-reports of absence because of illness of our respondents proved to be rather inaccurate. Underreporting of frequency and duration of sick leave was more common than overreporting. Therefore, both sources of error had a cumulative effect.While nonresponse did not result in biased relationships, recall errors had clearly biasing consequences: seven out of 30 correlation coefficients analyzed were too biased to produce valid outcomes; another six were substantially biased. Multiple regression used for predicting recent absence because of illness among our respondents also led to different outcomes depending on the choice of data source (administration or questionnaire) for our absence variables.     

集团化办学的内涵与功能

集团化办学是以职教组织为核心,以专业建设、人才培养、科技研发为主要纽带,以集团章程为共同行为规范的职业教育联合体。文章主要从集团化办学的内涵和功能进行了简单介绍。     

Sequential estimation of a location parameter and powers of a scale parameter from delayed observations

The problem of sequentially estimating a location parameter and powers of a scale parameter is considered in the case when the observations become available at random times. Certain classes of sequential estimation procedures are derived under an invariant balanced loss function and with the observation cost determined by a convex function of the stopping time and the number of observations up to that time.     

Neyman–Pearson Lemma for Fuzzy Hypotheses Testing with Vague Data

In hypotheses testing, such as other statistical problems, we may confront imprecise concepts. One case is a situation in which both hypotheses and observations are imprecise. This paper tries to develop a new approach for testing fuzzy hypothesis when the available data are fuzzy, too. First, some definitions are provided, such as: fuzzy sample space, fuzzy-valued random sample, and fuzzy-valued random variable. Then, the problem of fuzzy hypothesis testing with vague data is formulated. Finally, we state and prove a generalized Neyman–Pearson Lemma for such problem. The proposed approach is illustrated by some numerical examples.     

Strong uniform convergence for the estimator of the regression function under ϕ-mixing conditions

Suppose the observations (X _i,Y _i), i=1,…, n, are ϕ-mixing. The strong uniform convergence and convergence rate for the estimator of the regression function was studied by serveral authors, e.g. G. Collomb (1984), L. Gy?rfi et al. (1989). But the optimal convergence rates are not reached unless the Y _i are bounded or the E exp (a|Y _i|) are bounded for some a>0. Compared with the i.i.d. case the convergence of the Nadaraya-Watson estimator under ϕ-mixing variables needs strong moment conditions. In this paper we study the strong uniform convergence and convergence rate for the improved kernel estimator of the regression function which has been suggested by Cheng P. (1983). Compared with Theorem A in Y. P. Mack and B. Silverman (1982) or Theorem 3.3.1 in L. Gy?rfi et al. (1989), we prove the convergence for this kind of estimators under weaker moment conditions. The optimal convergence rate for the improved kernel estimator is attained under almost the same conditions of Theorem 3.3.2 in L. Gy?rfi et al. (1989). Received: September 1999     

A Microeconomic Analysis of Homelessness: An Empirical Investigation Using Choice-Based Sampling

This study estimates a structural model of the probability of homelessness by drawing data from two sources. The observations on the housed come from the American Housing Survey and the data on the homeless come from a separate study dealing exclusively with the homeless. Since the survey on the homeless targeted a larger fraction of that population, the sample is choice-based. The results suggest that older males with low incomes and high levels of depression are more likely to be homeless. Improvement in the number and quality of homeless shelters is expected to increase substantially the number of homeless. The policy simulations provide support for cash transfers to the very poor to reduce their likelihood of becoming homeless and for a weakening of housing codes to increase the availability of inexpensive, low-quality rental housing.     

浅谈假设检验中的两类错误及样本含量的关系

假设检验是统计推断的内容之一,统计推断在体育统计学中的地位也十分重要。在假设检验中存在两类错误。在很多时候,我们往往只注意第一类错误的控制,而对于第二类错误经常不考虑。其实,对于第二类错误的控制也是十分必要的。本文对于两类错误的成因以及如何控制第二类错误进行了探讨,希望对于第二类错误的控制提出一些解决的方法。     

Further thoughts on simplicity and complexity in population projection models

"This article is a review of--and response to--a special issue of Mathematical Population Studies that focused on the relative performance of simpler vs. more complex population projection models. I do not attempt to summarize or comment on each of the articles in the special issue, but rather present an additional perspective on several points: definitions of simplicity and complexity, empirical evidence regarding population forecast accuracy, the costs and benefits of disaggregation, the potential benefits of combining forecasts, criteria for evaluating projection models, and issues of economic efficiency in the production of population projections."     

Een opmerking over het aanpassen van functies aan een groot aantal waarnemingsuitkomsten

Note on the fitting of a function to a large number of observations.
The paper deals with various ways in which a set of functions may be chosen to describe a given body of observations, the parameters determining the function being determined by the data.
The special case when the functions of the set are given in the form of a table or a graph is emphasized.     

浅议降低51单片机定时器定时误差的几种方法

51单片机在当前控制检测系统中的应用越来越多,对其定时的精确要求也越来越高。虽然51单片机自带的16位定时/计数器较为精确,但是在实际应用过程中难免存在误差,而且这个误差不可避免,所以降低51单片机定时器误差就显得尤为重要。     

The price elasticity of the supply of single-family detached urban housing

Past attempts to estimate the price elasticity of the supply of housing have erred by using aggregate data. Many houses are built in areas where the volume of residential construction is low. Consequently, the influence of observations from higher-volume areas where costs may be higher is diminished. This problem is eliminated by using cross-sectional data from 61 different American urban areas, for a total of 223 observations from 1976 to 1981, to estimate a translog cost function for housing. The supply elasticity is found to be infinite.     

河北省阜平县电子政务发展存在的问题及对策分析

随着信息时代的到来,电子政务也越来越体现出其重要性。近年来,我国县级电子政务取得了不凡的成绩,但整体来看,其发展建设中仍存在一些问题和缺陷,本文以河北省阜平县为例,就这一问题提出了一些看法和建议。     

Nested Unobserved Heterogeneity not Orthogonal to Regressors

Many social phenomena are of a nested nature and recordedin hierarchical data, e.g., repeated observations of siblings (individual level) within families(context level). In these phenomena, unobserved heterogeneity can occur at both levels and may becorrelated with the regressors. This article addresses nested unobserved heterogeneity notorthogonal to the regressors, which is rarely discussed in the methodology literature. The articleextends the econometric one-factor fixed-effects approach to handle nested fixed effects.F tests for model comparisons are used to test whether the total heterogeneity exists and whetherthe total heterogeneity consists solely of contextual heterogeneity. It then introduces methods todecompose the two levels of heterogeneity and provides formal tests for each level andtheir relative importance, which are developed from classical ANOVA. To provide a stronger testfor time-varying context-specific heterogeneity, the article develops an estimator using thedifference-in-differences method. An empirical example of a study on child behavior problems isused to illustrate the methods introduced in the article.     

Bootstrap inference using estimating equations and data that are linked with complex probabilistic algorithms

Probabilistic record linkage is the act of bringing together records that are believed to belong to the same unit (e.g., person or business) from two or more files. It is a common way to enhance dimensions such as time and breadth or depth of detail. Probabilistic record linkage is not an error-free process and link records that do not belong to the same unit. Naively treating such a linked file as if it is linked without errors can lead to biased inferences. This paper develops a method of making inference with estimating equations when records are linked using algorithms that are widely used in practice. Previous methods for dealing with this problem cannot accommodate such linking algorithms. This paper develops a parametric bootstrap approach to inference in which each bootstrap replicate involves applying the said linking algorithm. This paper demonstrates the effectiveness of the method in simulations and in real applications.     

ARL-3460直读光谱仪的误差分析

原子发射光谱分析以其快速、准确性高、选择性高、多元素同时分析、线性范围广等特点而被广泛应用,在现代检测中发挥着重要的作用。但由于检测设备、氩气、制样过程、分析方法等因素产生误差,直接影响直读光谱仪分析结果的准确性。文章主要从设备、氩气状况、制样过程、分析方法四个方面出发,对直读光谱仪分析过程中的误差进行了分析,分析结果对光谱检测的准确性有一定的参考价值。