Another Remark on the Alternative Expectation Formula

Students in a calculus-based probability course will often see the expectation formula for nonnegative continuous random variables in terms of the survival function. This alternative expectation formula has a wide spectrum of applications. It is natural to ask whether there is a multivariate version of this formula. This note gives an affirmative answer by establishing such a formula using two different approaches. The two approaches employed in this note correspond to the two approaches for the univariate case. Supplementary materials for this article are available online.     

Multilevel models for repeated binary outcomes: attitudes and voting over the electoral cycle

Models for fitting longitudinal binary responses are explored by using a panel study of voting intentions. A standard multilevel repeated measures logistic model is shown to be inadequate owing to a substantial proportion of respondents who maintain a constant response over time. A multivariate binary response model is shown to be a better fit to the data.     

Managing the International Strategic Sourcing Process as a Market-Driven Organizational Learning System*

This study examines the effects of market-driven organizational learning on a select set of strategic sourcing outcomes involving the sourcing function of a Fortune 500 multinational corporation. The focus is on the dyadic activities and relationships between the domestic and international strategic business units (SBUs) and the corporate buying center. The hypothesized relationships are tested on the overall sample and based on a two-by-two matrix framework defined by international versus domestic settings and frequent versus infrequent sourcing scenarios. Based on a sample of 179 domestic and 167 international SBUs, the results suggest that market-driven organizational learning in the strategic sourcing units influences customer satisfaction, relationship commitment, and cycle time of the sourcing process. However, while the set of learning orientations appears to be strategically robust across the four quadrant scenarios (moderator settings), the sourcing situations differ somewhat in the specific tactical learning orientations preferred.     

Organizational Learning in Global Purchasing: A Model and Test of Internal Users and Corporate Buyers*

This research examines a model centered on organizational learning in purchasing. Two different studies are conducted to test the hypotheses among purchasing users (Study 1) and buyers (Study 2). The user sample consists of users representing 355 strategic business units of a Fortune 500 multinational corporation. The buyer sample consists of corporate buyers of 200 multinational corporations drawn from the membership directory of the National Association of Purchasing Management (NAPM). In each study, the focus is on the learning relationships between corporate buyers and internal users in the purchasing organization. Based on the two studies, the results suggest that organizational learning in the purchasing process is influenced by the organizational culture factors of localness, transformational leadership, and openness. Organizational learning has a positive effect on information processing in the purchasing system, which, in turn, has a positive influence on the cycle time of the purchasing process.     

一个新的稳健ARCH检验和YJ-GARCH模型

 众所周知,Engle (1982) 的ARCH检验对于条件均值模型误设并不稳健,特别地,当条件均值是非线性过程而我们仅对之建立线性模型时,它过度地拒绝真实的原假设,导致出现严重的水平扭曲 (size distortion)。因此,本文在文献当中首次利用Yeo-Johnson变换方法来转换均值模型的因变量以排除ARCH 过程中均值部分的非线性,进而提出一个新的稳健ARCH检验以及一个新的GARCH模型——Yeo-Johnson (YJ) GARCH模型。蒙特卡罗模拟结果表明,稳健的ARCH检验在水平 (size) 和势 (power) 方面的表现要显著优于Engle (1982) 的ARCH检验。对上证综指收益率的实证研究结果表明,YJ-GARCH模型的拟合效果要显著优于线性GARCH模型。     

Union-Intersection testing for outliers in multivariate normal data

The union-intersection approach to multivariate test construction is used to develop an alternative to Wilks' likelihood ratio test statistic for testing for two or more outliers in multivariate normal data. It is shown that critical values of both statistics are poorly approximated by Bonferroni bounds. Simulated critical values are presented for both statistics for significance levels 1% and 5%, for sample sizes 10(5)30, 40, 50, 75 and 100 for 2, 3, 4 and 5 dimensions. A power comparison of the two tests in the slippage of the mean model for generating outliers indicates that the union-intersection test is the more powerful when the slippages are close to collinear. Although Wilks' test remains the preference for general use, the union-intersection test could be valuable when such special structure in the data is suspected.     

基于ARCH类模型的国际粮价波动规律研究

粮价的波动最终会给一国的粮食安全带来巨大风险。了解国际粮价的波动特征有助于采取相应的措施稳定粮价,避免粮价波动的国际传导对国内粮食市场进而对粮食安全产生不利影响。通过建立ARCH类模型,分析各类粮食国际价格的波动规律。得出的主要结论有:国际粮价波动存在明显的集族性;外部冲击对国际粮价波动具有持久性影响;国际粮食市场不存在高风险高粮价的特征;国际粮价波动具有显著的非对称性,而且粮价上涨的信息引发的粮价波动要大于粮价下降的信息引发的波动。     

具有结构变化的资产定价模型的贝叶斯自回归条件异方差检验

在现代资产定价理论中,一个基本的假定是证券资产风险溢价满足方差齐性。然而,这样的假设未必是正确的,因此,需要对资产定价模型进行异方差的检验。本文在贝叶斯框架下考察了具有结构变化的资产定价模型,提出了检验该模型的回归条件异方差的贝叶斯检验方法。最后利用两个具体实例论证了所提方法的有效性。