When is n large enough? Looking for the right sample size to estimate proportions

The central limit theorem indicates that when the sample size goes to infinite, the sampling distribution of means tends to follow a normal distribution; it is the basis for the most usual confidence interval and sample size formulas. This study analyzes what sample size is large enough to assume that the distribution of the estimator of a proportion follows a Normal distribution. Also, we propose the use of a correction factor in sample size formulas to ensure a confidence level even when the central limit theorem does not apply for these distributions.     

Theoretical results on the discrete Weibull distribution of Nakagawa and Osaki

In this paper, we discuss some theoretical results and properties of the discrete Weibull distribution, which was introduced by Nakagawa and Osaki [The discrete Weibull distribution. IEEE Trans Reliab. 1975;24:300–301]. We study the monotonicity of the probability mass, survival and hazard functions. Moreover, reliability, moments, p-quantiles, entropies and order statistics are also studied. We consider likelihood-based methods to estimate the model parameters based on complete and censored samples, and to derive confidence intervals. We also consider two additional methods to estimate the model parameters. The uniqueness of the maximum likelihood estimate of one of the parameters that index the discrete Weibull model is discussed. Numerical evaluation of the considered model is performed by Monte Carlo simulations. For illustrative purposes, two real data sets are analyzed.     

局部平稳部分线性面板数据模型的统计推断

部分线性模型是一类非常重要的半参数回归模型,由于它既含有参数部分又含有非参数部分,与常规的线性模型相比具有更强的适应性和解释能力。文章研究带有局部平稳协变量的固定效应部分线性面板数据模型的统计推断。首先提出一个两阶段估计方法得到模型中未知参数和非参数函数的估计,并证明估计量的渐近性质,然后运用不变原理构造出非参数函数的一致置信带,最后通过数值模拟研究和实例分析验证了该方法的有效性。     

Identifying as an evidence-based social worker: the influence of attitudes,access, confidence,and education

This study explored United States-based social workers’ (N = 152) attitudes toward, access to, and confidence in engaging in evidence-based practice (EBP), the extent to which social work education prepared them to engage in EBP, and the factors that contributed to their identification as an evidence-based practitioner. Findings indicated that although practitioners had a positive attitude toward engaging in EBP, they were only moderately confident in doing so, rarely accessed evidence, and were only moderately prepared through their education. Believing that EBP should be implemented, more educational preparation, and positive attitudes contributed to greater identification as an evidence-based practitioner, areas that social work and continuing education should further support to enhance social workers’ EBP skills.     

信心、货币政策与中国经济波动关系的统计检验

文章基于时变视角,依据行为经济学理论,构建了一个包含企业家信心、投资者信心、利率、货币增长率、经济增长率和通货膨胀率六变量的TVP-VAR模型,研究信心、货币政策与经济波动之间的时变特征。结果表明:企业家信心和投资者信心能够影响利率和货币增长率,即信心可以通过影响货币政策进而作用于宏观经济。货币增长率和利率能够影响投资者信心和企业家信心,进而可以通过信心影响宏观经济。从时变角度看,企业家信心一单位的正向冲击在整个样本区间内均会促进经济的增长;在短期内投资者信心和货币增长率对经济增长具有促进作用,但是在长期内货币增长率的提高会阻碍经济的增长。     

Assessing the Performance of a Classification‐Based Vulnerability Analysis Model

In this article, a classification model based on the majority rule sorting (MR‐Sort) method is employed to evaluate the vulnerability of safety‐critical systems with respect to malevolent intentional acts. The model is built on the basis of a (limited‐size) set of data representing (a priori known) vulnerability classification examples. The empirical construction of the classification model introduces a source of uncertainty into the vulnerability analysis process: a quantitative assessment of the performance of the classification model (in terms of accuracy and confidence in the assignments) is thus in order. Three different app oaches are here considered to this aim: (i) a model–retrieval‐based approach, (ii) the bootstrap method, and (iii) the leave‐one‐out cross‐validation technique. The analyses are presented with reference to an exemplificative case study involving the vulnerability assessment of nuclear power plants.     

大学生学科文化自信培育的价值逻辑及路径探析 ——以河北工程大学地球科学与工程学院为例

学科文化是学科的灵魂，是学科不断发展创新的精神源泉和内在动力。学科文化自信是文化自信的重要组成部分，培育大学生文化自信应着眼全局，整体推进。学科文化自信与文化自信具有统一性，与核心价值观培育具有同构性，与担当民族复兴大任具有生成性。培育大学生学科文化自信，要深入挖掘和整合学科文化内涵，不断创新和发展培育手段，最终达到浸润和形塑博学自信的新时代大学生的目标。学科文化自信的培育可以达到激发学生学术热情，促进学生和学科全面发展，弘扬社会主义核心价值观，坚定理想信念以及践行使命担当的效用。     

历史变局、国家兴衰与发展之路——三次千年变局叠加下的中国特色社会主义发展道路

每当先进的发展制度开始取代落后的发展制度时，整个世界格局就会进入重大的转换阶段。在中国五千年的发展历史中，有两次重大的历史变局完全改变了中国历史发展轨迹并深远地影响了当前中国的发展模式。新时代下的中国作为前两次历史变局影响的客体，曾经既是先进发展制度取代落后发展制度的受益者，也经历过作为落后发展制度主体而被先进发展制度冲击的过程。目前世界正处于第三次先进发展制度与落后发展制度交替的历史变局阶段，作为第三次重大历史变局的主体，在三次千年历史变局叠加的背景下，能否有效地认识、适应并改造利用前两次历史变局的经验与教训，构建系统性、科学性、可行性、领先性的中国特色社会主义制度，将决定中国在本次历史变局中能否顺利成为先进发展制度的主体从而实现民族复兴。     

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.