Hypothesis test for paired samples in the presence of missing data

Missing data are present in almost all statistical analysis. In simple paired design tests, when some subject has one of the involved variables missing in the so-called partially overlapping samples scheme, it is usually discarded for the analysis. The lack of consistency between the information reported in the univariate and multivariate analysis is, perhaps, the main consequence. Although the randomness on the missing mechanism (missingness completely at random) is an usual and needed assumption for this particular situation, missing data presence could lead to serious inconsistencies on the reported conclusions. In this paper, the authors develop a simple and direct procedure which allows using the whole available information in order to perform paired tests. In particular, the proposed methodology is applied to check the equality among the means from two paired samples. In addition, the use of two different resampling techniques is also explored. Finally, real-world data are analysed.     

Confidence Intervals for the Hyperparameters in Structural Models

This article deals with the bootstrap as an alternative method to construct confidence intervals for the hyperparameters of structural models. The bootstrap procedure considered is the classical nonparametric bootstrap in the residuals of the fitted model using a well-known approach. The performance of this procedure is empirically obtained through Monte Carlo simulations implemented in Ox. Asymptotic and percentile bootstrap confidence intervals for the hyperparameters are built and compared by means of the coverage percentages. The results are similar but the bootstrap procedure is better for small sample sizes. The methods are applied to a real time series and confidence intervals are built for the hyperparameters.     

A Revisit to the Behrens–Fisher Problem: Comparison of Five Test Methods

We revisit the well-known Behrens–Fisher problem and apply a newly developed ‘Computational Approach Test’ (CAT) to test the equality of two population means where the populations are assumed to be normal with unknown and possibly unequal variances. An advantage of the CAT is that it does not require the explicit knowledge of the sampling distribution of the test statistic. The CAT is then compared with three widely accepted tests—Welch–Satterthwaite test (WST), Cochran–Cox test (CCT), ‘Generalized p-value’ test (GPT)—and a recently suggested test based on the jackknife procedure, called Singh–Saxena–Srivastava test (SSST). Further, model robustness of these five tests are studied when the data actually came from t-distributions, but wrongly perceived as normal ones. Our detailed study based on a comprehensive simulation indicate some interesting results including the facts that the GPT is quite conservative, and the SSST is not as good as it has been claimed in the literature. To the best of our knowledge, the trends observed in our study have not been reported earlier in the existing literature.     

Detecting Directionality in Time Series

Abstract

Directionality can be seen in many stationary time series from various disciplines, but it is overlooked when fitting linear models with Gaussian errors. Moreover, we cannot rely on distinguishing directionality by comparing a plot of a time series in time order with a plot in reverse time order. In general, a statistical measure is required to detect and quantify directionality. There are several quite different qualitative forms of directionality, and we distinguish: rapid rises followed by slow recessions; rapid increases and rapid decreases from the mean followed by slow recovery toward the mean; directionality above or below some threshold; and intermittent directionality. The first objective is to develop a suite of statistical measures that will detect directionality and help classify its nature. The second objective is to demonstrate the potential benefits of detecting directionality. We consider applications from business, environmental science, finance, and medicine. Time series data are collected from many processes, both natural and anthropogenic, by a wide range of organizations, and directionality can easily be monitored as part of routine analysis. We suggest that doing so may provide new insights to the processes.     

Confidence intervals for impulse responses under departures from normality

Monte Carlo evidence shows that in structural VAR models with fat-tailed or skewed innovations the coverage accuracy of impulse response confidence intervals may deterorate substantially compared to the same model with Gaussian innovations. Empirical evidance suggests that such departures from normality are quite plausible for economic time series. The simulation results suggest that applied researchers are best off using nonparametric bootstrap intervals for impulse responses, regardless of whether or not there is evidence of fat tails or skewness in the error distribution. Allowing for departures from normality is shown to considerably weaken the evidence of the delayed overshooting puzzle in Eichenbaum and Evans (1995).     

农地抵押贷款信用评价体系构建

通过构建农地抵押贷款信用评价体系,为贷款申请人信用资质的判定提供客观标准。借鉴Z评分模型,使用Bootstrap方法筛选农地抵押贷款信用评价指标,并使用基于离差最大的组合赋权法确定各指标的权重。在信用评价模型建立后,通过贷款户和申请被拒农户信用评分的差异,划定优质借款人的信用评分范围,最后对该信用评分模型的有效性进行了检验。     

Asymptotic Distributions of Quasi‐Maximum Likelihood Estimators for Spatial Autoregressive Models

This paper investigates asymptotic properties of the maximum likelihood estimator and the quasi‐maximum likelihood estimator for the spatial autoregressive model. The rates of convergence of those estimators may depend on some general features of the spatial weights matrix of the model. It is important to make the distinction with different spatial scenarios. Under the scenario that each unit will be influenced by only a few neighboring units, the estimators may have ‐rate of convergence and be asymptotically normal. When each unit can be influenced by many neighbors, irregularity of the information matrix may occur and various components of the estimators may have different rates of convergence.     

Simple and effective number-of-bins circumference selectors for a histogram

Two very effective data-based procedures which are simple and fast to compute are proposed for selecting the number of bins in a histogram. The idea is to choose the number of bins that minimizes the circumference (or a bootstrap estimate of the expected circumference) of the frequency histogram. Contrary to most rules derived in the literature, our method is therefore not dependent on precise asymptotic analyses. It is shown by means of an extensive Monte-Carlo study that our selectors perform well in comparison with recently suggested selectors in the literature, for a wide range of density functions and sample sizes. The behaviour of one of the proposed rules is also illustrated on real data sets.     

数字经济、空间效应与全要素生产率

当前,数字经济蓬勃发展,已成为经济增长的新动能。本文从数字产业化与产业数字化 两个维度,采用主成分分析法构建了数字经济发展水平的指标体系,并利用2004-2017年我国省际面板 数据,在克服内生性问题的基础上,实证分析了数字经济发展对全要素生产率的影响。研究发现,数字 经济发展显著促进了全要素生产率的提升。但较之高生产率地区和东部地区,数字经济发展对低生产率地区和中西部地区全要素生产率的提升作用更大。就机制而言,人力资本投资与产业结构升级是数 字经济影响全要素生产率的两个渠道。进一步的空间计量分析表明,数字经济发展不仅会提升本地区 的全要素生产率,还存在显著的空间溢出效应,有助于提升邻近地区的全要素生产率。本文的研究为评估数字经济发展的影响效果提供了数据支撑和分析视角,也为探寻全要素生产率的提升路径提供了政策参考。     

Reexamining the ethnic hierarchy of locational attainment: Evidence from Los Angeles

Because of a lack of data, the locational attainment literature has not incorporated documentation status into models examining group differences in neighborhood quality. I fill this void by using the Los Angeles Family and Neighborhood Survey, which permits the identification of undocumented respondents, allowing a reexamination of the ethnic structure of locational attainment in this important immigrant-receiving city. Results first suggest that while undocumented Latinos live in the poorest quality communities, blacks live in neighborhoods that are similar to native-born Latinos and better than foreign-born Asians and Latinos. Second, the effects of education are strongest for blacks, allowing the highly educated an opportunity to reside in communities that are of better quality than educated Latinos and Asians. Thus, undocumented Latinos replace blacks at the bottom of the locational attainment hierarchy, allowing educated blacks in Los Angeles to reside in better neighborhoods than blacks in the nation at large.