Balance and randomness in sequential clinical trials: the dominant biased coin design

Efron's biased coin design (BCD) is a well‐known randomization technique that helps neutralize selection bias, while keeping the experiment fairly balanced for every sample size. Several extensions of this rule have been proposed, and their properties were analyzed from an asymptotic viewpoint and compared via simulations in a finite setup. The aim of this paper is to push forward these comparisons by taking also into account the adjustable BCD, which is never considered up to now. Firstly, we show that the adjustable BCD performs better than Efron's coin with respect to both loss of precision and randomness. Moreover, the adjustable BCD is always more balanced than the other coins and, only for some sample sizes, slightly more predictable. Therefore, we suggest the dominant BCD, namely a new and flexible class of procedures that can change the allocation rule step by step in order to ensure very good performance in terms of both balance and selection bias for any sample size. Our simulations demonstrate that the dominant BCD is more balanced and, at the same time, less or equally predictable than Atkinson's optimum BCD. Copyright © 2014 John Wiley & Sons, Ltd.     

Efficient MCMC sampling in dynamic mixture models

We show how to improve the efficiency of Markov Chain Monte Carlo (MCMC) simulations in dynamic mixture models by block-sampling the discrete latent variables. Two algorithms are proposed: the first is a multi-move extension of the single-move Gibbs sampler devised by Gerlach, Carter and Kohn (in J. Am. Stat. Assoc. 95, 819–828, 2000); the second is an adaptive Metropolis-Hastings scheme that performs well even when the number of discrete states is large. Three empirical examples illustrate the gain in efficiency achieved. We also show that visual inspection of sample partial autocorrelations of the discrete latent variables helps anticipating whether blocking can be effective.     

From an Agrarian to an Environmental,Food, and Natural Resource Base for Agricultural Policy: Some Reflections on the Case of the EC

Abstract The agriculture of the European Community (EC) has experienced significant changes in the last decade. From a situation of deficiency in agricultural and food production, the twelve-nation community has shifted to a situation of food overproduction. This change has also been characterized by a rapid decrease in the agricultural labor force and a decrease of its importance in the employment structure which has manifested itself in fewer, more efficient farms. This alteration of structural conditions has led to the emergence of a new set of agricultural issues. This article discusses these changes by underscoring the decline of agrarian-based issues and the emergence of environmental, food, and natural resource-based issues. It is maintained that EC agricultural policies have been instrumental in both the resolution of agrarian-based issues and in the creation of new problems embodied in the environmental, food, and natural resource-based policies. The combination of the demise of agrarian-based policies and the emergence of environmental, food, and natural resource-based policies is also employed as a theoretical perspective from which the evolution of the agricultural sector in the EC can be interpreted.     

The debate on young people and participatory citizenship. Questions and research prospects

For quite some time, experts and policy-makers in Western societies have been looking at young people with concern, extending their analysis from the potential for conflict and divergence, to socio-cultural dynamics and inter-generational relations. There is certainly intense debate as to how close or distant young people are to forms and content of citizenship as experienced in the creation of modern democracy. Such a debate, developed at both the institutional and the scientific level, focuses particularly on concepts of participation and active citizenship and identifies in the civic engagement and participatory citizenship of young people the key factors for the maintenance of democracy and social cohesion. By bringing to light the meanings, implications, and ambivalences of the concepts at the centre of the debate, also with a view to European policies, the article aims at highlighting rhetoric, voids, and emerging contradictions and pointing out questions and possible research paths.     

The Interactive Effects of Job Resources and Motivations to Volunteer Among a Sample of Italian Volunteers

The examination of organizational features of voluntary associations and their effects on the experiences of volunteers traditionally received less attention than other topics. This paper aimed to examine how different features as social and task support, information and appreciation affect volunteers’ experiences in terms of job satisfaction, organizational commitment, and intention to remain. Moreover, potential moderating effects by motivations to volunteer in relation to the abovementioned relations were tested. Through the use of a self-report questionnaire, distributed among 162 Italian voluntary associations (final sample of 1,445 volunteers), structural equation modeling (SEM), and moderated-SEM were carried out to verify hypothesized associations and potential moderations. Job resources were associated with the three outcomes, moreover many moderating effects by the values/understanding and career motivations were found. The results were commented on the basis of the current literature, and some practical suggestions were drawn about voluntary associations’ management and volunteers’ recruitment and selection.     

An Analysis of Extremely High Nineteenth-Century Winter Neonatal Mortality in a Local Context of Northeastern Italy

Beginning in the mid-seventeenth century, infant mortality in Veneto (a region in northeastern Italy) began to increase, starting at 250?? and rising to 350?? by the mid-nineteenth century??one of the highest levels ever recorded in modern Europe. This dramatic change??in a period of worsening economic conditions??was due to variations in winter neonatal mortality, which was 3?C4 times higher in Veneto than in other areas with similar winter temperatures (such as England). We combine micro-data on neonatal mortality with daily data on temperatures for a specific context during the period of 1816?C1868 characterized by very high neonatal mortality. We find that the risk of death was particularly intense during the first week of life and strongly correlated with external minimum temperature. Through a comparison of these results with other findings in the literature, we suggest that the increase in winter neonatal mortality in Veneto could have principally been caused by the deteriorating physical condition of mothers, lessening the ??quality?? of infants who consequently were quite susceptible to cold temperatures.     

Knightian Analysis of the Vickrey Mechanism

We analyze the Vickrey mechanism for auctions of multiple identical goods when the players have both Knightian uncertainty over their own valuations and incomplete preferences. In this model, the Vickrey mechanism is no longer dominant‐strategy, and we prove that all dominant‐strategy mechanisms are inadequate. However, we also prove that, in undominated strategies, the social welfare produced by the Vickrey mechanism in the worst case is not only very good, but also essentially optimal.     

Hidden information problems in the design of family allowances

We consider the optimal determination of family allowances in a model where some of the parents have higher ability to raise children than others. First-best policy gives both types of parents the same level of utility. If neither parental ability nor parental actions are fully observable, however, the policy maker has to take into account the incentive-compatibility constraint that more able parents should not find it profitable to mis-represent their true ability by investing less in their children, and having a lower number of children. The second-best policy induces more able parents to have the first-best number of children, and to invest in each child at the first-best level. Less able parents are induced to have fewer children than in first best, and will underinvest in each child. Whether the government should subsidize more the more able parents, or the less able ones, depends on the properties of the cost function. In second best, however, less able parents will end up with lower utility than more able parents whatever the cost function.All correspondence to Annalisa Luporini. The paper has benefitted from comments by three anonymous referees. Responsible editor: Junsen Zhang.     

A model with long-term survivors for the analysis of current-status nuptiality data

The model proposed in this paper combines a logistic regression model and a Weibull regression model for the analysis of current-status data. This joint model allows a simultaneous estimation of two sets of effects on the covariates: one on the probability that the event occurs (also known as quantum) and the other on the timing of the event. Thus, the model can be seen either as an extension of a survival-analysis model for use with current-status data where a survival fraction is added in order explicitly to take into account the possibility that the event may never occur, or as an extension of survival analysis with long-term survivors to the analysis of current-status data. As an illustrative application we apply our model to a study of nuptiality in seventeenth-century Italy.     

The Effect of Couple Disagreement about Child‐Timing Intentions: A Parity‐Specific Approach

Using couple data from a longitudinal study conducted in Italy, a country with persistently low fertility levels, we examined the effect of partners' discrepant child‐timing intentions on reproductive behavior. We found that the effect of couple disagreement on subsequent fertility is parity‐specific and does not depend on whether only the male or the female partner intends to have a(nother) child. The disagreement tends to produce an intermediate childbearing outcome at parities zero and one, while the outcome is shifted more toward agreement on not having a(nother) child at parity two. The empirical evidence suggests that gender equality in reproductive decisionmaking is not driven by partners' equal bargaining power or partners' equal access to economic resources. The findings indicate that the predictive power of child‐timing intentions strongly improves if both partners' views are considered in fertility models, and thus support the adoption of couple analysis in fertility research.