Regularization through variable selection and conditional MLE with application to classification in high dimensions

It is often the case that high-dimensional data consist of only a few informative components. Standard statistical modeling and estimation in such a situation is prone to inaccuracies due to overfitting, unless regularization methods are practiced. In the context of classification, we propose a class of regularization methods through shrinkage estimators. The shrinkage is based on variable selection coupled with conditional maximum likelihood. Using Stein's unbiased estimator of the risk, we derive an estimator for the optimal shrinkage method within a certain class. A comparison of the optimal shrinkage methods in a classification context, with the optimal shrinkage method when estimating a mean vector under a squared loss, is given. The latter problem is extensively studied, but it seems that the results of those studies are not completely relevant for classification. We demonstrate and examine our method on simulated data and compare it to feature annealed independence rule and Fisher's rule.     

Approximate sorting of data streams with limited storage

We consider the problem of approximate sorting of a data stream (in one pass) with limited internal storage where the goal is not to rearrange data but to output a permutation that reflects the ordering of the elements of the data stream as closely as possible. Our main objective is to study the relationship between the quality of the sorting and the amount of available storage. To measure quality, we use permutation distortion metrics, namely the Kendall tau, Chebyshev, and weighted Kendall metrics, as well as mutual information, between the output permutation and the true ordering of data elements. We provide bounds on the performance of algorithms with limited storage and present a simple algorithm that asymptotically requires a constant factor as much storage as an optimal algorithm in terms of mutual information and average Kendall tau distortion. We also study the case in which only information about the most recent elements of the stream is available. This setting has applications to learning user preference rankings in services such as Netflix, where items are presented to the user one at a time.     

Product Positioning Using a Self‐Organizing Map and the Rings of Influence

In this article, we propose a new product positioning method based on the neural network methodology of a self‐organizing map. The method incorporates the concept of rings of influence, where a firm evaluates individual consumers and decides on the intensity to pursue a consumer, based on the probability that this consumer will purchase a competing product. The method has several advantages over earlier work. First, no limitations are imposed on the number of competing products and second, the method can position multiple products in multiple market segments. Using simulations, we compare the new product positioning method with a quasi‐Newton method and find that the new method always approaches the best solution obtained by the quasi‐Newton method. The quasi‐Newton method, however, is dependent on the initial positions of the new products, with the majority of cases ending in a local optimum. Furthermore, the computational time required by the quasi‐Newton method increases exponentially, while the time required by the new method is small and remains almost unchanged, when the number of new products positioned increases. We also compute the expected utility that a firm will provide consumers by offering its products. We show that as the intensity with which a firm pursues consumers increases, the new method results in near‐optimal solutions in terms of market share, but with higher expected utility provided to consumers when compared to that obtained by a quasi‐Newton method. Thus, the new method can serve as a managerial decision‐making tool to compare the short‐term market share objective with the long‐term expected utility that a firm will provide to consumers, when it positions its products and intensifies its effort to attract consumers away from competition.     

Knowing Your Adversary: Israeli Structure of Political Opportunity and the Inception of the Palestinian Intifada

Social movement scholars have suggested that opportunity structures are not objective features of the world but must be constructed by social forces, including social movements. Here, we attempt to analyze how Palestinians living in the occupied territories constructed political opportunity during the run-up to the 1987 first Intifada. We analyze how the changing Israeli political opportunity structure affected Palestinians’ framing of the structural conditions they faced. In particular, we examine (1) how the consolidating Palestinian movement within the occupied territories built the capacity for a shared, collective framing of events, and (2) how the movement adapted a strategy based on its understanding of the opportunity presented by divisions in Israeli society concerning the occupation. Based on the analysis, we offer several insights into the Intifada's dynamics and trajectories.

Determinants of the health and survival of the elderly: Suggestions from two different experiences — Italy and Israel

This study compares the health status and survival of the elderly in two countries, Italy and Israel. While both are developed Mediterranean countries, their degree of ageing, characteristic features of the elderly, health status and survival are different. The data are from two sample surveys and, for Israel, from a record linkage between survey and mortality data at five years remove. A preliminary analysis, using a multiple correspondence factorial analysis, highlighted a gradual change in living arrangements and socio-economic features as the population ages, which was only slightly associated with health conditions. In Israel, moreover, the Arab minority differs according to social conditions, living arrangements and health status. The determinants of health status and survival of the elderly in both countries were studied using as dependent variables; 1) self-perceived health status, 2) the frequency of medical examinations; 3) medical tests, for both countries and 4) (for Israel) deaths. Linear logistic models were constructed using, as explanatory variables, sex, age and living arrangements, a variable indicative of community level socio-economic and cultural conditions, two indicators describing individual socio-economic conditions and smoking habits. Thus it is possible to assess the impact of explanatory variables by comparing both subjective conditions and behaviour factors regarding medical care, with the unequivocal confirmation provided by death.     

Creating places,relationships and education for refugee children in camps: Lessons learnt from the ‘The School of Peace’ educational model

This paper describes a unique model for building an afternoon school for refugee children sustained by volunteers and refugee teachers and based on humanistic intercultural values. The methodology is participatory including the whole school, from children to teachers to volunteers and managers. Central themes in the findings include a synergetic focus on creative placemaking, conflict negotiation and formal studies. This points to a theoretical connection between informal and formal studies. The findings teach us about the needs of refugee children. A methodological contribution is the use of arts-based methods to capture refugee children's lived experiences of school.     

Ordering of Sequentially Sampled Exponential Experiments

Let X ₁, X ₂, ... be a sequence of i.i.d. random variables, X _i∼ F _θ, θ∈Θ. Let N ₁ and N ₂ be two stopping rules. For a class of exponential families { F _θ: θ∈Θ} we show that the experiment Y ₁ = ( X ₁, ..., X _N1) carries more statistical information than Y ₂ = ( X ₁, ..., x _N2) only if N ₁ is stochastically larger then N ₂     

Making sense of ‘Price Tag’ violence: changing contexts,shifting strategies,and expanding targets

Writings on the fringe Jewish settler grassroots network known as the Hilltop Youth have proliferated in recent years, following the increase in violent activism associated with the network. But knowledge on this violent activism, called Price Tag, has remained conflicting and problematic. Central questions persist: What is the meaning of Price Tag violence? What explains the increase in the rate and salience of Price Tag violence? What are the social-political implications of Price Tag violence? This article argues that Price Tag violence represents a new strategy of contention taking shape in the context of a fundamental reconfiguration of relations within Israel’s institutional and non-institutional radical Right, and that it represents a highly consequential social and political phenomenon with destabilizing and destructive effects nationally and regionally.     

Relational dynamics in factional adoption of terrorist tactics: a comparative perspective

Scholars of political terrorism generally agree that the radical group is usually a splinter faction of an opposition movement. Seldom, however, is an attempt made to incorporate insights and tools from the literature on social movements and contentious politics into the study of the process by which a faction splinters from the larger opposition movement and adopts terrorist tactics—a process commonly known as radicalization. Drawing upon the relational approach from the literature on contentious politics, this article seeks to further understanding of radicalization by examining how and when relational mechanisms, operating in their respective relational arenas, interact and combine to drive it. Proposed is a relational framework for a comparative analysis of radicalization at three levels—domestic, ethno-national, and international—employing the case of the Weather Underground, Fatah-Tanzim, and al-Qaeda respectively.