Model selection in high-dimensional noisy data: a simulation study

In many practical applications, high-dimensional regression analyses have to take into account measurement error in the covariates. It is thus necessary to extend regularization methods, that can handle the situation where the number of covariates p largely exceed the sample size n, to the case in which covariates are also mismeasured. A variety of methods are available in this context, but many of them rely on knowledge about the measurement error and the structure of its covariance matrix. In this paper, we set the goal to compare some of these methods, focusing on situations relevant for practical applications. In particular, we will evaluate these methods in setups in which the measurement error distribution and dependence structure are not known and have to be estimated from data. Our focus is on variable selection, and the evaluation is based on extensive simulations.     

Incorporating human sexuality content into a positive youth development framework: Implications for community prevention

As approaches to positive youth development (PYD) gain momentum, the issue of sexuality – a critical component of human development – is being subsumed by ideological debates. In the current political climate, sexuality education is often relegated to biological and/or values-based approaches, neglecting essential relational and collective aspects of sexuality. Through the explication of sexuality as an important component of youth's social ecology, this paper provides a conceptual link between the goals of the Sexuality Information and Education Council of the United States' (SIECUS) Guidelines for comprehensive sexuality education and those of PYD. We argue that sexuality, as a normative part of human development, culture, identity, and relationships, be approached from an asset-based perspective, rather than a deficit-based perspective. We propose a framework that illustrates how aspects of sexuality are embedded within PYD contexts, and demonstrates how a sexuality education program rooted in SIECUS guidelines can further PYD goals across community contexts.     

Improved Approximation for Breakpoint Graph Decomposition and Sorting by Reversals

Sorting by Reversals (SBR) is one of the most widely studied models of genome rearrangements in computational molecular biology. At present, is the best known approximation ratio achievable in polynomial time for SBR. A very closely related problem, called Breakpoint Graph Decomposition (BGD), calls for a largest collection of edge disjoint cycles in a suitably-defined graph. It has been shown that for almost all instances SBR is equivalent to BGD, in the sense that any solution of the latter corresponds to a solution of the former having the same value. In this paper, we show how to improve the approximation ratio achievable in polynomial time for BGD, from the previously known to for any > 0. Combined with the results in (Caprara, Journal of Combinatorial Optimization, vol. 3, pp. 149–182, 1999b), this yields the same approximation guarantee for n! – O((n – 5)!) out of the n! instances of SBR on permutations with n elements. Our result uses the best known approximation algorithms for Stable Set on graphs with maximum degree 4 as well as for Set Packing where the maximum size of a set is 6. Any improvement in the ratio achieved by these approximation algorithms will yield an automatic improvement of our result.     

Psychosocial contexts of the homosexuality of Filipino men in heterosexual unions

The Philippines is one developing country in which a systematic inquiry on the homosexuality of men in heterosexual consensual union is rare. With the thought that the public can be guided more knowledgeably in forming some responsible knowledge and opinion about homosexual men's lives within heterosexual unions, a small-scale exploratory study was carried out and completed in 1997 among 15 married or co-habiting men in Metro Manila, the Philippines. The research delved into respondents' sexual histories; their perceptions of own homosexual attraction, desire and orientation; and their reasons, motivations and expectations for marrying or cohabiting. It also looked into respondents' reports of whether their partners knew their sexual orientation; respondents' roles and responsibilities in household management and decision making; and effects of respondents' homosexuality on marital and familial relationships.     

Bayesian bivariate survival analysis using the power variance function copula

Copula models have become increasingly popular for modelling the dependence structure in multivariate survival data. The two-parameter Archimedean family of Power Variance Function (PVF) copulas includes the Clayton, Positive Stable (Gumbel) and Inverse Gaussian copulas as special or limiting cases, thus offers a unified approach to fitting these important copulas. Two-stage frequentist procedures for estimating the marginal distributions and the PVF copula have been suggested by Andersen (Lifetime Data Anal 11:333–350, 2005), Massonnet et al. (J Stat Plann Inference 139(11):3865–3877, 2009) and Prenen et al. (J R Stat Soc Ser B 79(2):483–505, 2017) which first estimate the marginal distributions and conditional on these in a second step to estimate the PVF copula parameters. Here we explore an one-stage Bayesian approach that simultaneously estimates the marginal and the PVF copula parameters. For the marginal distributions, we consider both parametric as well as semiparametric models. We propose a new method to simulate uniform pairs with PVF dependence structure based on conditional sampling for copulas and on numerical approximation to solve a target equation. In a simulation study, small sample properties of the Bayesian estimators are explored. We illustrate the usefulness of the methodology using data on times to appendectomy for adult twins in the Australian NH&MRC Twin registry. Parameters of the marginal distributions and the PVF copula are simultaneously estimated in a parametric as well as a semiparametric approach where the marginal distributions are modelled using Weibull and piecewise exponential distributions, respectively.     

Dealing with the biased effects issue when handling huge datasets: the case of INVALSI data

The increasing prevalence of huge datasets addresses the research to appropriate statistical methods for solving troubles caused by their complexity. On the one hand, several techniques are mentioned in the literature, especially for the time-consuming and variables reduction issues. On the other, less debate is devoted to the statistical inference issue. Indeed, a large number of involved statistical units may lead to wrongly consider as significant variables without any actual impact on the phenomenon under study. This paper suggests a suitable subsampling procedure for the reduction of the number of statistical units and provides a novel index for the assessment of the significance effects. The proposal is validated by comparing results obtained from the analysis on the original data to those obtained from the proposed subsampling approach. The illustrative application focuses on the educational dataset made available by the National Committee for the Evaluation of the Italian Education Systems (INVALSI). This dataset collects information about the student features and achievements in Maths within the lower secondary schools of the Lombardy region (Italy). Due to the hierarchical structure of the data, a multilevel model is implemented with the purpose of investigating the effects of both individual and school factors on student Maths score.     

The multiattribute evaluation of program-planning contractors

This note describes how the theory of measurable multiattribute value functions was used to evaluate the proposals of three competing subcontractors for a program-planning project undertaken by Los Alamos National Laboratory. The purpose of the program-planning project was to develop a methodology for the evaluation of alternative long-range strategies for the achievement of controlled thermonuclear fusion. A measurable multiattribute value function was developed based on eleven criteria. Eight judges made evaluations on each of these criteria, and their judgments were synthesized to identify the winning subcontractor. While we emphasize details associated with this specific application, we expect the problem structure and methodology to be amenable to other contractor-and proposal-evaluation efforts after only minor modifications.     

Communicate over a network: the blog as a ‘new’ social space

The contribution analyzes from a sociological perspective the development of the blog, passing through the different typologies, to define the relationship that develops in today's society between the network and the individual, through a theoretical comparison of the major scholars who have dealt with the issue of network. From Sherry Turkle to Manuel Castells up to the studies of Barry Wellman, we will define the development of the network as a new social space. The work incorporates some classical theories of Simmel, some by Goffman and Thompson about interaction, of community-society by Töennies and the action-system of Luhmann. The central part of the article focuses on how the space of the network can become, in some cases, a ‘place’ of sharing not only of entertainment topics but also of those that have some importance for public opinion. Then the blog becomes a ‘showcase’ in which to expose the peculiar characteristics of one's identity, but also a point of listening for those who do not have easy access to traditional media. Through the testimony of two young people, we will highlight those aspects that characterize the blog as a communication tool, from the diary to the letter, as well as the role played by these documentary sources in the past in sociology's field. In this way, some salient points arise about the use of the network space, compared to traditional media. The last part of the contribution proposes a comparison between America and Japan about the use of blogs and social networks, no longer in numerical terms, but proposing a reflection that brings out an individual who, as a sociable being, exploits all the possible ways to communicate, feeling in such situations freer to express his emotions, and able build a dialogue that turns out to be an added value to his person and in relationship with others outside.