Estimation of contingency tables in complex survey sampling using probabilistic expert systems

In this paper we explore the possibility to use a particular class of models, known as probabilistic expert systems, to define two classes of estimators of a contingency table in case of stratified sampling designs. The two classes are characterized by the different role of the sampling design: in the first, the sampling design is treated as an additional variable; in the second, it is used only for estimation purposes by means of the survey weights. The bias/variance trade off of these estimators is analyzed and the consequences of model misspecification are illustrated. Furthermore, it is shown that the Horvitz–Thompson estimator belongs to both classes of estimators. It comes out that the Horvitz–Thompson estimator is almost always inefficient but robust. Monte Carlo simulations illustrate the efficiency of the proposed estimators.     

Decision‐making in drug development using a composite definition of success

Evidence‐based quantitative methodologies have been proposed to inform decision‐making in drug development, such as metrics to make go/no‐go decisions or predictions of success, identified with statistical significance of future clinical trials. While these methodologies appropriately address some critical questions on the potential of a drug, they either consider the past evidence without predicting the outcome of the future trials or focus only on efficacy, failing to account for the multifaceted aspects of a successful drug development. As quantitative benefit‐risk assessments could enhance decision‐making, we propose a more comprehensive approach using a composite definition of success based not only on the statistical significance of the treatment effect on the primary endpoint but also on its clinical relevance and on a favorable benefit‐risk balance in the next pivotal studies. For one drug, we can thus study several development strategies before starting the pivotal trials by comparing their predictive probability of success. The predictions are based on the available evidence from the previous trials, to which new hypotheses on the future development could be added. The resulting predictive probability of composite success provides a useful summary to support the discussions of the decision‐makers. We present a fictive, but realistic, example in major depressive disorder inspired by a real decision‐making case.     

Vanishing financial contagion?

While a number of crises in emerging markets generated widespread contagion in financial markets during the 1990s, more recent crises (notably, in Argentina) have been mostly contained within national borders. This has led some observers to wonder whether contagion might have become a feature of the past, with financial markets now better discriminating between emerging countries with good and bad fundamentals. Available data suggest that the main channels that contribute to transmitting financial crises across countries are – if anything – even stronger today than in the 1990s. Moreover, anticipation by international investors may help to explain the near-absence of contagion in the context of the Argentine crisis. This paper argues that a prudent working assumption is that financial contagion has not vanished.     

How far from identifiability? A systematic overview of the statistical matching problem in a non parametric framework

Statistical matching consists in estimating the joint characteristics of two variables observed in two distinct and independent sample surveys, respectively. In a parametric setup, ranges of estimates for non identifiable parameters are the only estimable items, unless restrictive assumptions on the probabilistic relationship between the non jointly observed variables are imposed. These ranges correspond to the uncertainty due to the absence of joint observations on the pair of variables of interest. The aim of this paper is to analyze the uncertainty in statistical matching in a non parametric setting. A measure of uncertainty is introduced, and its properties studied: this measure studies the “intrinsic” association between the pair of variables, which is constant and equal to 1/6 whatever the form of the marginal distribution functions of the two variables when knowledge on the pair of variables is the only one available in the two samples. This measure becomes useful in the context of the reduction of uncertainty due to further knowledge than data themselves, as in the case of structural zeros. In this case the proposed measure detects how the introduction of further knowledge shrinks the intrinsic uncertainty from 1/6 to smaller values, zero being the case of no uncertainty. Sampling properties of the uncertainty measure and of the bounds of the uncertainty intervals are also proved.     

A Measure of the Cultural Distance Between Countries

The current study was an investigation of age and gender differences in the relation between students’ school-related social support (i.e., teacher support and classmate support) and subjective well-being (SWB) in school (i.e., school satisfaction and affect in school), as well as the developmental differences in SWB in school. Data were collected from a sample of 2,158 students in Grades 4 through 11 in China on two separate occasions, 6-weeks apart. The findings indicated older age students reported lower levels of SWB in school than younger students. Furthermore, girls reported higher levels of school satisfaction than boys. In addition, both teacher support and classmate support significantly related to school satisfaction at Time 2 (controlling for Time 1) for all students. Classmate support significantly related to affect in school at Time 2 for all students, whereas teacher support only significantly related to affect in school at Time 2 for elementary school students. Specifically, teacher support accounted for the larger amount of variance in school satisfaction at Time 2 for elementary and high school students. Gender moderated the relation between teacher support and school satisfaction at Time 2 for elementary school students, as well as the relation between classmate support and school satisfaction at Time 2 for middle school students. Implications based on developmental considerations were discussed.     

Independence Structure of Natural Conjugate Densities to Exponential Families and the Gibbs' Sampler

In this paper the independence between a block of natural parameters and the complementary block of mean value parameters holding for densities which are natural conjugate to some regular exponential families is used to design in a convenient way a Gibbs' sampler with block updates. Even when the densities of interest are obtained by conditioning to zero a block of natural parameters in a density conjugate to a larger "saturated" model, the updates require only the computation of marginal distributions under the "unconditional" density. For exponential families which are closed under marginalization, including both the zero mean Gaussian family and the cross-classified Bernoulli family such an implementation of the Gibbs' sampler can be seen as an Iterative Proportional Fitting algorithm with random inputs.     

Supply chain contamination: An exploratory approach on the collateral effects of negative corporate events

The present work investigates the impact of negative events on supply chain partners. Through a contextualised discussion of the literature on supply chains and on the efficient market hypothesis, it is proposed that negative events negatively impact the market value of suppliers and customers. Following an exploratory approach, 307 companies (21 source companies, 158 suppliers and 128 customers) comprehending 20 cases of environmental disaster, corporate social irresponsibility, operational failure, corporate fraud and corruption were analysed. Results show that in 12 out of the 20 cases investigated supply chain partners indeed had their market value penalised, encompassing, to a greater or lesser degree, all five categories of cases considered. Yet, while both suppliers and customers absorbed the outcomes of negative events, suppliers seem to be at greater risk of sustaining such losses. Likewise, cases in which the source companies were also negatively affected seem to be slightly more prone to cause losses among suppliers and customers. In this sense, the concept of supply chain contamination is coined to address the observed outcomes. The study offers new insights into the applicability of the efficient market hypothesis and contributes to the assessment of the dissemination of negative events in supply chains, a theme that, despite its potential detrimental consequences for firms and stakeholders, has not yet been sufficiently treated in the Management literature.     

Network,exposure and rhetoric: Italian occupational fields and heterogeneity in constructing the globalized self

Drawing on the findings of a broad inter‐university research programme conducted in Italy, in this article we explore how individuals' transnational networks combine with other dimensions of their social experience in the production of a self‐perception of their own ‘global identity’. In particular, attention is focused on the structures and social spaces of everyday life in five crucial occupations (corporate managers, financial services workers, artists, media professionals and schoolteachers) where people's professional action is performed simultaneously along local and global axes. Within these groups the globalized self does not merely reflect individuals' engagement in transnational networks, but is also the outcome of a complex process including two added dimensions of social life in the job setting: (1) the degree and type of non‐filtered exposure to pressures stemming from the global environment, which both constrain and enable subjective practices of coping with change and ambiguity; and (2) the degree and type of competence in the rhetorics of globalization, namely the level of access to well‐known repertoires of interpretive resources for making sense of global trends. This analysis is consistent with social science conceptualizations arguing for a more nuanced understanding of globalization. In this light, not only is globalization a multidimensional process but it also produces a variety of responses and meanings by differently positioned actors.     

New results on the convergence of random matrices

This paper extends the previous convergence results in Cerqueti and Costantini (2008) to a more general case using larger normed set of functions. In this regard, the weight-based convergence of the random matrices and their generalized eigenvalues is obtained under less restrictive requirements for the weights.     

Group testing with test error as a function of concentration

A common assumption in group testing applications is that there is no test error, i.e., misclassification of a single item or a group of items cannot occur. Graff and Roeloffs ( 1972 ) have proposed a procedure applicable when there is a known probability of misclassification. We generalize their results to the situation where the probability of misclassification depends on the proportion of defective items in the group.