A Graphical Tool for Interpreting Regression Coefficients of Trinomial Logit Models

Multinomial logit (also termed multi-logit) models permit the analysis of the statistical relation between a categorical response variable and a set of explicative variables (called covariates or regressors). Although multinomial logit is widely used in both the social and economic sciences, the interpretation of regression coefficients may be tricky, as the effect of covariates on the probability distribution of the response variable is nonconstant and difficult to quantify. The ternary plots illustrated in this article aim at facilitating the interpretation of regression coefficients and permit the effect of covariates (either singularly or jointly considered) on the probability distribution of the dependent variable to be quantified. Ternary plots can be drawn both for ordered and for unordered categorical dependent variables, when the number of possible outcomes equals three (trinomial response variable); these plots allow not only to represent the covariate effects over the whole parameter space of the dependent variable but also to compare the covariate effects of any given individual profile. The method is illustrated and discussed through analysis of a dataset concerning the transition of master’s graduates of the University of Trento (Italy) from university to employment.     

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.     

20世纪三四十年代宁夏水利建设述论

20世纪三四十年代 ,宁夏地方当局等推出一系列水利建设措施 ,这既意味着宁夏水利事业的近代化开始初露端倪 ,也促使宁夏平原农田引黄灌溉得以延续 ,并对宁夏地方经济的恢复、初兴与抗日战争等具有促进作用     

我国产业间波及效应的探讨

从理论上来说,某一产业的变化会引起其它产业间的连锁反映。产业间的波及效应可以通过投入系数表来加以分析。通过实证分析,研究我国产业间波及效应的强弱,可以为国家制定产业政策、优化产业结构提供依据。     

数字金融对农户气候适应性行为的影响

气候适应性技术采用率低下已成为制约农业可持续发展的重要因素,数字金融可能影响农户的气候适应性行为。基于河南、陕西、山西三省1 384份农户微观调查数据,运用内生转换回归模型构建反事实分析框架,实证分析数字金融使用对农户气候适应性行为的影响效应及其作用机制。研究发现:使用数字金融能显著促进农户气候适应性技术采纳行为,具体表现为在反事实假设下,使用数字金融的农户若未使用其气候适应性技术采纳程度将下降;未使用数字金融的农户如果使用了,其气候适应性技术采纳程度将上升。机制分析表明,数字金融能够提高借贷易得性与信息易得性,进而促进农户采纳气候适应性行为,农户对于金融包容性的认知能够正向增强数字金融对农户气候适应性行为的影响效应。异质性分析表明,数字金融使用对于资本型适应性行为影响的边际效应最大,在反事实假设下也表现为数字金融使用对农户资本型适应性行为提升效果最强;数字金融对农业收入占家庭收入比率较高、接受过培训的农户采纳气候适应性技术促进效应更高。     

Median treatment effect in randomized trials

For two response variables y _t and y _c corresponding to two treatments for two policies) T and C , we wish to learn about quantiles of y _t− y _c from the marginal quantiles of y _t and y _c; only one of y _t and y _c is observed for an individual. We find that, in general, this is difficult for quantiles other than the median unless strong assumptions are imposed on how y _t is related to y _c. For the median, we present conditions under which the sign of the median treatment effect is identified.     

科学技术批判思潮的理论误区及其有效性意义

西方思想家对科学技术的批判表达了对技术异化现象的不满与抗议。在一些重大的问题上,西方的科学技术批判思潮并没有击中技术异化的要害。科学技术作为人的一种理性活动,是人们实现实践目标的工具和手段。因而,技术在本质上,是中性的。技术异化的根源在于人的活动本身。但是,我们也必须正视科学技术批判思潮的有限性意义以及合理性。对技术使用的负面效应必须有清醒的认识。     

网络动态海报《随传随到》的多模态话语分析

作为数字传播时代的新兴产物,动态海报具有画面表现力强、传递信息量大、受众参与度高等特征,已广泛应用于网络广告领域。研究基于多模态话语分析综合理论框架,辅之以视觉语法理论,解析网络动态海报《随传随到》运用多模态符号资源实现的积极广告传播效果。研究发现：文化层面,意识形态是理解动态海报和实现广告传播效果的必要前提;语境层面,语境因素是动态海报产生特征和积极广告传播效果的动因;内容层面,广告传播效果取决于多模态资源在意义构建中的运用;表达层面,GIF格式文件为动态海报达到积极广告传播效果提供了技术支持。研究结合广告学知识探索了多模态话语分析在网络动态海报中的应用,旨在为动态海报的广告传播效果提供语言学解释。     

考虑脉冲现象的复杂供应链系统及其稳定策略

供应链系统是一个复杂的系统,一方面由于时间延迟、信息不对称及反馈机制等,会产生牛鞭效应,另一方面供应链具有需求突增或骤减的脉冲特点,上述现象都可能导致供应链系统混沌,而现有的供应链模型仅考虑了“牛鞭效应”,并未考虑脉冲现象对供应链系统的影响。文章建立了考虑脉冲现象的供应链模型,分析了脉冲现象对供应链系统的影响,并给出了使供应链系统稳定的策略,讨论了参数扰动对该模型的影响,通过数值算例验证了稳定策略的有效性。研究发现:脉冲现象对供应链系统有着显著影响,但只要选取恰当的脉冲强度和脉冲时间间隔,供应链系统是可以稳定的。     

Active‐controlled,non‐inferiority trials in oncology: arbitrary limits,infeasible sample sizes and uninformative data analysis. Is there another way?

In oncology, it may not always be possible to evaluate the efficacy of new medicines in placebo-controlled trials. Furthermore, while some newer, biologically targeted anti-cancer treatments may be expected to deliver therapeutic benefit in terms of better tolerability or improved symptom control, they may not always be expected to provide increased efficacy relative to existing therapies. This naturally leads to the use of active-control, non-inferiority trials to evaluate such treatments. In recent evaluations of anti-cancer treatments, the non-inferiority margin has often been defined in terms of demonstrating that at least 50% of the active control effect has been retained by the new drug using methods such as those described by Rothmann et al., Statistics in Medicine 2003; 22:239-264 and Wang and Hung Controlled Clinical Trials 2003; 24:147-155. However, this approach can lead to prohibitively large clinical trials and results in a tendency to dichotomize trial outcome as either 'success' or 'failure' and thus oversimplifies interpretation. With relatively modest modification, these methods can be used to define a stepwise approach to design and analysis. In the first design step, the trial is sized to show indirectly that the new drug would have beaten placebo; in the second analysis step, the probability that the new drug is superior to placebo is assessed and, if sufficiently high in the third and final step, the relative efficacy of the new drug to control is assessed on a continuum of effect retention via an 'effect retention likelihood plot'. This stepwise approach is likely to provide a more complete assessment of relative efficacy so that the value of new treatments can be better judged.