Robustness and Corrections for Sample Size Adaptation Strategies Based on Effect Size Estimation

A study on the robustness of the adaptation of the sample size for a phase III trial on the basis of existing phase II data is presented—when phase III is lower than phase II effect size. A criterion of clinical relevance for phase II results is applied in order to launch phase III, where data from phase II cannot be included in statistical analysis. The adaptation consists in adopting the conservative approach to sample size estimation, which takes into account the variability of phase II data. Some conservative sample size estimation strategies, Bayesian and frequentist, are compared with the calibrated optimal γ conservative strategy (viz. COS) which is the best performer when phase II and phase III effect sizes are equal. The Overall Power (OP) of these strategies and the mean square error (MSE) of their sample size estimators are computed under different scenarios, in the presence of the structural bias due to lower phase III effect size, for evaluating the robustness of the strategies. When the structural bias is quite small (i.e., the ratio of phase III to phase II effect size is greater than 0.8), and when some operating conditions for applying sample size estimation hold, COS can still provide acceptable results for planning phase III trials, even if in bias absence the OP was higher.

Main results concern the introduction of a correction, which affects just sample size estimates and not launch probabilities, for balancing the structural bias. In particular, the correction is based on a postulation of the structural bias; hence, it is more intuitive and easier to use than those based on the modification of Type I or/and Type II errors. A comparison of corrected conservative sample size estimation strategies is performed in the presence of a quite small bias. When the postulated correction is right, COS provides good OP and the lowest MSE. Moreover, the OPs of COS are even higher than those observed without bias, thanks to higher launch probability and a similar estimation performance. The structural bias can therefore be exploited for improving sample size estimation performances. When the postulated correction is smaller than necessary, COS is still the best performer, and it also works well. A higher than necessary correction should be avoided.     

A consistent method of estimation for the parameters of the three-parameter inverse Gaussian distribution

In this paper, we propose a consistent method of estimation for the parameters of the three-parameter inverse Gaussian distribution. We then discuss some properties of these estimators and show by means of a Monte Carlo simulation study that the proposed estimators perform better than some other prominent estimators in terms of bias and root mean squared error. Finally, we present two real-life examples to illustrate the method of inference developed here.     

数字经济对我国市域农业经济韧性的影响效应与机理分析——基于系统GMM模型与动态门槛模型的检验

基于2011—2019年我国277个市域农业的面板数据,运用反事实方法科学测度了其经济韧性水平,并借助系统GMM模型、中介模型和动态门槛模型等方法,实证检验了数字经济对市域农业经济韧性的影响效应及作用机理。研究发现：数字经济显著增强了市域农业经济韧性,这一结论经一系列稳健性检验后仍能成立;机制分析结果表明,农业资本深化是数字经济提升市域农业经济韧性的重要路径。异质性分析表明,在东部、中部、西部地区和人力资本水平较高的地区,数字经济对市域农业经济韧性的影响效应更为显著,而对东北部地区的提升效应则不显著。动态门槛检验进一步揭示,数字经济对市域农业经济韧性的影响呈现边际递增的非线性特征,当数字经济发展水平越过特定门槛值（0147）时,数字经济对市域农业经济韧性的促进作用显著增强。     

Does the twin deficit hypothesis hold in the OECD countries under different real interest rate regimes?

This paper explores the validity of the twin deficit hypothesis in selected 25 OECD countries with annual data for 2005–2016 by considering different real interest rate regimes. A non-dynamic panel threshold model, introduced by Hansen (1999), is employed. The novelty of the empirical findings from the present study is that there exists a non-linear relationship between the budget deficit and the trade balance, which is driven by a critical threshold level in the real interest rates. The findings suggest that twin deficit hypothesis holds only under the low real interest rate regime, that is, rises in budget deficits lead to deteriorations in the trade balance when the real interest rate is below the threshold level. When the high real interest rate (i.e. above-the-threshold) regime is concerned, increasing budget deficits give rise to improvements in the trade balance, a finding consistent with the twin divergence hypothesis. Thus, the effect on the trade balance of an expansionary fiscal policy that worsens the budget balance reverses substantially depending on the threshold level of the real interest rates. The major policy implication of this paper is that the policy makers in the selected OECD countries should pay a greater attention to fiscal discipline in order to prevent the trade balance from worsening, because the majority of the countries fall into the low real interest rate regime over the recent years of the sample period (i.e. between 2010 and 2016).     

Availability analysis for general repairable systems with repair time threshold

Availability analysis is an important issue in many practical fields. This paper investigates the availability for general repairable systems with repair time threshold. Based on practical applications, a repair time threshold is introduced. If the period of a repair is less than a predefined time threshold, then the system may be considered as working during this period, i.e., the effect of the repair could be neglected. Otherwise, if the period of a repair is longer than the given threshold, then the system is considered as working from the beginning of the system failure until the repair time exceeding the threshold, i.e., the time point of the system down could be delayed. We consider both constant and random repair time threshold. This paper valuates the user-perceived availability, when the user does not experience any service interruption because the duration of repair is too short. The results can be applied in reliability engineering, queueing theory and many other fields. A numerical example for ventilator system is presented to demonstrate the application of the developed approach.     

中国全要素农田水利效率的地区差异和门槛效应研究

农田水利作为我国农业基础设施投资的重要组成部分,对农业经济增长及农民增收具有重要影响。基于DEA在全要素生产的框架,构建全面衡量我国农田水利效率的指标——全要素农田水利效率,选取2001—2015年省级面板数据,运用DEA Malmquist方法测算31个省的全要素农田水利效率,并对不同区域农田水利效率进行对比分析。研究结果表明我国全要素农田水利效率存在明显地区差异,东北地区效率最高、超过农业大省聚集的华东和华中地区;全要素农田水利效率与区域经济发展水平存在不完全匹配现象,主要与农田水利效率及影响因素之间的非线性关系有关。基于农田水利效率省际差异,采用门槛回归模型检验影响全要素农田水利效率的门槛特征,研究结果显示：农村经济发展水平对农田水利全要素生产率存在显著的收敛门槛效应、机械动力投入对农田水利全要素生产率存在明显的加速门槛效应。     

环境规制工具对中国经济增长的影响——基于环境分权的门槛效应分析

基于环境分权体制,使用2001—2012年中国30个省份的面板数据,运用系统广义矩估计考察环境规制工具的经济增长效应,并基于不同环境分权检验了环境规制工具与经济增长的非线性关系。研究结果表明:（1）环境分权下,命令控制型和公众参与型规制工具的经济促进效应由负转正,而市场激励型规制工具则由正转负;（2）三类环境规制工具对经济增长的影响均存在双重门槛效应,只有环境分权越过特定临界值时才能引致正向的经济增长效应;（3）在命令控制型规制工具上,有15个省份处于合理水平,而在市场激励型和公众参与型规制工具上,有8个省份处于合理水平。因此,为实现环境保护和经济协调发展,政府应合理优化规制工具组合和深化改革环境分权结构。     

人员流动对组织间隐性知识共享影响研究

促进组织间隐性知识共享是一个企业取得成功的关键.隐性知识和人与人之间传染病的传播途径非常相似,主要是通过人与人之间的直接接触进行传播的.文章受传染病动力学建模思想的启发,针对有人员相互流动的两个组织,并考虑员工的引入和离职,构建了两组织间的隐性知识传播动力学模型,给出区分实现组织间隐性知识共享与否的阈值,并对模型进行数值仿真以验证所得理论结果的正确性.从理论性定量研究的角度说明,在两组织间适当进行人员流动能有效促进组织间隐性知识共享,而如果人员流动不合理则会起到抑制作用.     

Social Indeterminacy

An extension of Condorcet's paradox by McGarvey (1953) asserts that for every asymmetric relation R on a finite set of candidates there is a strict‐preferences voter profile that has the relation R as its strict simple majority relation. We prove that McGarvey's theorem can be extended to arbitrary neutral monotone social welfare functions that can be described by a strong simple game G if the voting power of each individual, measured by the Shapley–Shubik power index, is sufficiently small. Our proof is based on an extension to another classic result concerning the majority rule. Condorcet studied an election between two candidates in which the voters' choices are random and independent and the probability of a voter choosing the first candidate is p>1/2. Condorcet's jury theorem asserts that if the number of voters tends to infinity then the probability that the first candidate will be elected tends to one. We prove that this assertion extends to a sequence of arbitrary monotone strong simple games if and only if the maximum voting power for all individuals tends to zero.     

马克思哲学研究的诠释视域及其误区

马克思哲学在东西方的不同历史文化语境下的不同诠释,造就马克思哲学的不同历史命运。对马克思哲学的研究必须从对马克思哲学的诠释与反思入手,找到探究马克思哲学的新的诠释理路,为马克思主义哲学的进一步发展探索出一条可能的路向。