Bayesian and Dominant‐Strategy Implementation in the Independent Private‐Values Model

We prove—in the standard independent private‐values model—that the outcome, in terms of interim expected probabilities of trade and interim expected transfers, of any Bayesian mechanism can also be obtained with a dominant‐strategy mechanism.     

Accuracy of edge detection methods with local information in speckled imagery

We compare the accuracy of five approaches for contour detection in speckled imagery. Some of these methods take advantage of the statistical properties of speckled data, and all of them employ active contours using B-spline curves. Images obtained with coherent illumination are affected by a noise called speckle, which is inherent to the imaging process. These data have been statistically modeled by a multiplicative model using the G0 distribution, under which regions with different degrees of roughness can be characterized by the value of a parameter. We use this information to find boundaries between regions with different textures. We propose and compare five strategies for boundary detection: three based on the data (maximum discontinuity on raw data, fractal dimension and maximum likelihood) and two based on estimates of the roughness parameter (maximum discontinuity and anisotropic smoothed roughness estimates). In order to compare these strategies, a Monte Carlo experience was performed to assess the accuracy of fitting a curve to a region. The probability of finding the correct edge with less than a specified error is estimated and used to compare the techniques. The two best procedures are then compared in terms of their computational cost and, finally, we show that the maximum likelihood approach on the raw data using the G0 law is the best technique.     

Impact of selection bias on the evaluation of clusters of chemical compounds in the drug discovery process

Expert opinion plays an important role when selecting promising clusters of chemical compounds in the drug discovery process. Indeed, experts can qualitatively assess the potential of each cluster, and with appropriate statistical methods, these qualitative assessments can be quantified into a success probability for each of them. However, one crucial element often overlooked is the procedure by which the clusters are assigned to/selected by the experts for evaluation. In the present work, the impact such a procedure may have on the statistical analysis and the entire evaluation process is studied. It has been shown that some implementations of the selection procedure may seriously compromise the validity of the evaluation even when the rating and selection processes are independent. Consequently, the fully random allocation of the clusters to the experts is strongly advocated. Copyright © 2014 John Wiley & Sons, Ltd.     

A maximal domain of preferences for strategy-proof,efficient, and simple rules in the division problem

The division problem consists of allocating an amount M of a perfectly divisible good among a group of n agents. Sprumont (1991) showed that if agents have single-peaked preferences over their shares, the uniform rule is the unique strategy-proof, efficient, and anonymous rule. Ching and Serizawa (1998) extended this result by showing that the set of single-plateaued preferences is the largest domain, for all possible values of M, admitting a rule (the extended uniform rule) satisfying strategy-proofness, efficiency and symmetry. We identify, for each M and n, a maximal domain of preferences under which the extended uniform rule also satisfies the properties of strategy-proofness, efficiency, tops-onlyness, and continuity. These domains (called partially single-plateaued) are strictly larger than the set of single-plateaued preferences. However, their intersection, when M varies from zero to infinity, coincides with the set of single-plateaued preferences.An earlier version of this paper circulated under the title A maximal domain of preferences for tops-only rules in the division problem. We are grateful to an associate editor of this journal for comments that helped to improve the presentation of the paper and to Matt Jackson for suggesting us the interest of identifying a maximal domain of preferences for tops-only rules. We are also grateful to Dolors Berga, Flip Klijn, Howard Petith, and a referee for helpful comments. The work of Alejandro Neme is partially supported by Research Grant 319502 from the Universidad Nacional de San Luis. The work of Jordi Massó is partially supported by Research Grants BEC2002-02130 from the Spanish Ministerio de Ciencia y Tecnología and 2001SGR-00162 from the Generalitat de Catalunya, and by the Barcelona Economics Program of CREA from the Generalitat de Catalunya. The paper was partially written while Alejandro Neme was visiting the UAB unde r a sabbatical fellowship from the Generalitat de Catalunya.     

An information-theoretic approach to surrogate-marker evaluation with failure time endpoints

Over the last decades, the evaluation of potential surrogate endpoints in clinical trials has steadily been growing in importance, not only thanks to the availability of ever more potential markers and surrogate endpoints, also because more methodological development has become available. While early work has been devoted, to a large extent, to Gaussian, binary, and longitudinal endpoints, the case of time-to-event endpoints is in need of careful scrutiny as well, owing to the strong presence of such endpoints in oncology and beyond. While work had been done in the past, it was often cumbersome to use such tools in practice, because of the need for fitting copula or frailty models that were further embedded in a hierarchical or two-stage modeling approach. In this paper, we present a methodologically elegant and easy-to-use approach based on information theory. We resolve essential issues, including the quantification of “surrogacy” based on such an approach. Our results are put to the test in a simulation study and are applied to data from clinical trials in oncology. The methodology has been implemented in R.     

Educational Progress and Parenting Among Mexican Immigrant Mothers of Young Children

This study examined the potential for educational investments in Mexican immigrant mothers to enhance their management of their children's pathways through the educational system in the United States, which often disadvantages them. We tested this hypothesis with data on 816 Mexican immigrant women and their children from the Early Childhood Longitudinal Study–Kindergarten Cohort (ECLS‐K). The results suggest that mothers who pursued their own schooling over a 4‐year period, regardless of whether they obtained a degree, increased their engagement with their children's schools during that same period. The results appear to be robust to a wide range of factors that select women into continuing education.     

Exploring dialogic strategies in social media for fostering citizens’ interactions with Latin American local governments

Although the benefits of social media for enhancing citizens’ interactions with their local governments are well known in a more global context, few studies have focused on Latin America, or on the MERCOSUR countries in particular. This paper examines the use of dialogic strategies in the social media activities of local governments in MERCOSUR countries in order to generate citizens’ online engagement. Analysis of this question enhances our understanding of the use of social media by local governments in less developed countries and highlights the need for empirical evidence on the use of dialogic communication theory regarding stakeholder engagement with social media. The findings obtained reflect the positive influence of dialogic strategies on citizens’ online engagement, particularly those based on dialogic loop, useful information and generation of return visits, aimed at fostering participation via social media.     

Factors in educational exclusion: including the voice of the youth

The processes of educational exclusion are multiple and diverse. Research has shown that exclusion from school goes far beyond access. It is associated with crucial issues related to educational processes (belonging, recognition or representation) and results (knowledge or certificates). The objective of this article is to delve into the analysis of factors in educational exclusion, including the voice of the youth, as a key element in understanding these factors. The article begins with a literature review addressing the meaning, mechanisms and profiles of educational exclusion. It then presents qualitative fieldwork, consisting of six focus groups of young people (aged 14–24) who have been excluded from mainstream educational institutions in Barcelona, Spain. The results of the empirical analysis point to four critical elements in the process of educational exclusion as experienced by the youth: educational transitions; the role of teachers; the impact of grouping practices and disciplinary mechanisms; and the contrast between mainstream educational institutions and alternative learning arenas. By including the voice of the youth, the article provides a better understanding of the factors contributing to educational exclusion so as to advance in the construction of an educational system able to guarantee students’ right to learn and succeed in school.     

What is the right way to protest? On the process of justification of protest,and its relationship to the propensity to participate in different types of protest

This study explores how citizens in Spain perceive different tactics employed in anti-austerity protests in 2011–2013, and tests the model of the process of justification of protest. This model combines the elements of Gamson’s collective action frames theory (effectiveness, anger and grievances, operationalized as appraisal of harm) with the concept of legitimacy. It also links justification to the intention to participate. We empirically differentiate between three protest tactics: normative demonstrations, non-normative peaceful strategies, and non-normative violent actions. We find that demonstrations are perceived to be more legitimate, but less effective than non-normative peaceful protests. Violent strategies, on the other hand, are seen to be more effective than legitimate. We postulate and find that legitimacy and effectiveness partially or fully mediate the impact of political ideology, anger, and appraisal of harm on the probability of participation in non-normative protest. Finally, we establish meaningful differences in the predictors of the likelihood of joining normative, non-normative peaceful, or non-normative violent protests. Overall, our results suggest that the study of justification of collective action and especially, the inclusion of the notion of legitimacy, enriches our understanding of the popular approval of and propensity to participate in different forms of collective protest.