Skewness of maximum likelihood estimators in dispersion models

We introduce the dispersion models with a regression structure to extend the generalized linear models, the exponential family nonlinear models (Cordeiro and Paula, 1989) and the proper dispersion models (Jørgensen, 1997a). We provide a matrix expression for the skewness of the maximum likelihood estimators of the regression parameters in dispersion models. The formula is suitable for computer implementation and can be applied for several important submodels discussed in the literature. Expressions for the skewness of the maximum likelihood estimators of the precision and dispersion parameters are also derived. In particular, our results extend previous formulas obtained by Cordeiro and Cordeiro (2001) and Cavalcanti et al. (2009). A simulation study is performed to show the practice importance of our results.     

Reliability and Validity of the European Portuguese Version of the Social Touch Questionnaire

Social touch is essential for physical and emotional well-being. However, different meanings can be attributed to physical contact during social interactions and may generate bonding or avoidant behaviors. This personal and unique experience is not usually taken into account in health and social care services. The aim of this study is to produce a valid and reliable European Portuguese version of the Social Touch Questionnaire (STQ, Wilhelm et al. in Biol Psychol 58:181–202, 2001. doi: 10.1016/S0301-0511(01)00113-2). The STQ is a self-report questionnaire for adolescents and adults measuring behaviors and attitudes towards social touch. The original version was translated into European Portuguese using a forward-back translation process and its feasibility was examined. To evaluate the psychometric properties, a total of 242 Portuguese university students participated in the study (21.3 ± 3.8 years). The STQ was considered feasible, showed adequate internal consistency (Cronbach’s α = .734), and the test–retest correlation with the STQ items demonstrated a high concordance between the tests over a two-week interval (ICC = .990; n = 50). Validity tests were performed, comparing the total score of the STQ with that of the anxiety and avoidance subscales of the Social Interaction and Performance Anxiety and Avoidance Scale (SIPAAS). A very significant conceptual convergence was confirmed between the STQ and with the SIPAAS-Anxiety (r = .64; p < .0001) and with the SIPAAS-Avoidance (r = .59; p < .0001). The exploratory factor analysis, with Promax rotation, revealed 3 factors: dislike of physical touch, liking of familiar physical touch and liking of public physical touch (Cronbach’s alphas ranged from .68 to .75). Psychometric properties confirmed the adaptation of the STQ to the Portuguese culture. It is a reliable and valid self-report questionnaire and it appears to be a useful tool to assess behaviors and attitudes towards social touch.     

Modeling the impact of social discrimination on the physical and mental health of Portuguese gay,lesbian and bisexual people

Background: Despite growing acceptance of same-sex sexuality in Portugal, identity development of lesbian, gay and bisexual (LGB) individuals is still restricted by negative societal attitudes, which maintain the experience of stigmatization and discrimination. The purpose of this study is to document the frequency of discriminatory events experienced by sexual minorities and their association with indicators of physical and mental health in Portugal. Methods: A total of 610 LGB participants completed an online survey (mean age?=?34.48, SD?=?11.54). Most participants were single and self-identified as gay (73.8%). The survey included five categories of survey items: demographic information, social support, physical health, mental health, and discrimination experiences. Results: Physical and mental health results revealed that bisexual people were more likely to report higher levels of psychological distress than gay men. Overall, between one-fifth and one-fourth of the participants in this sample frequently felt the need to hide their sexual orientation to prevent discrimination experiences across the different settings. Regarding actual discrimination experiences, close to 20% reported having suffered from verbal abuse, followed by close to 10% who suffered from written threats, harassment, and physical threats. A hierarchical multiple regression analysis was performed to assess the effects of anticipated and actual discrimination on mental health. Possible confounding variables were added in the first block – age, sexual orientation, being in a relationship, body mass index, and HIV status. Anticipated and actual discrimination experiences were added in the second block. The first block of the analysis explained 6% of the overall variance, while the second block – discrimination experiences – explained an additional 17%. Conclusion: Portuguese culture and stigma/discrimination create discriminatory experiences which impact LGB people's health. Unless policies are changed to allow for the acceptance of LGB people, they will continue to experience violence and discrimination as a result of homophobia.     

The impacts of rapid demographic transition on family structure and income inequality in Brazil, 1981–2011

This study analysed the impact of changing family structure on income distribution. Specifically, it analysed how changes in the proportions of different categories of family in the population contributed to increases in the income of the richest and poorest social strata in Brazil, and the consequent impacts on income inequality. Rural and urban families were compared in order to understand how these dynamics had different impacts on more developed (urban) and less developed (rural) areas. The results emphasize how changes observed in family structure are more pronounced among the richest families, contributing to an increase in (i) the income of the richest families and (ii) income inequality between the richest and poorest families, as well as between urban and rural areas.     

New perspective on the benefits of the gene–environment independence in case–control studies

We study the benefit of exploiting the gene–environment independence (GEI) assumption for inferring the joint effect of genotype and environmental exposure on disease risk in a case–control study. By transforming the problem into a constrained maximum likelihood estimation problem we derive the asymptotic distribution of the maximum likelihood estimator (MLE) under the GEI assumption (MLE‐GEI) in a closed form. Our approach uncovers a transparent explanation of the efficiency gained by exploiting the GEI assumption in more general settings, thus bridging an important gap in the existing literature. Moreover, we propose an easy‐to‐implement numerical algorithm for estimating the model parameters in practice. Finally, we conduct simulation studies to compare the proposed method with the traditional prospective logistic regression method and the case‐only estimator. The Canadian Journal of Statistics 47: 473–486; 2019 © 2019 Statistical Society of Canada     

On scale-mixture Birnbaum–Saunders distributions

We present for the first time a justification on the basis of central limit theorems for the family of life distributions generated from scale-mixture of normals. This family was proposed by Balakrishnan et al. (2009) and can be used to accommodate unexpected observations for the usual Birnbaum–Saunders distribution generated from the normal one. The class of scale-mixture of normals includes normal, slash, Student-t, logistic, double-exponential, exponential power and many other distributions. We present a model for the crack extensions where the limiting distribution of total crack extensions is in the class of scale-mixture of normals.     

Asymptotic properties of MLE for partially observed fractional diffusion system with dependent noises

The paper studies long time asymptotic properties of the maximum likelihood estimator (MLE) for the signal drift parameter in a partially observed fractional diffusion system with dependent noise. Using the method of weak convergence of likelihoods due to Ibragimov and Khasminskii [1981. Statistics of Random Processes. Springer, New-York], consistency, asymptotic normality and convergence of the moments are established for MLE. The proof is based on Laplace transform computations which was introduced in Brouste and Kleptsyna [2008. Asymptotic properties of MLE for partially observed fractional diffusion system, preprint].     

Things Temporal Exposé, Passages from Benjamin

Nineteenth-century Paris was for Walter Benjamin the site of a singular historical event, the ur-form of bourgeois modernity. It was a “hellish” time disastrously bent on repeating itself and yet a threshold of great promise and possibility. By focusing on Benjamin's 1935 and 1939 Exposés for The Arcades Project, my paper develops the keywords of the Exposés (Arcades, Fashion, etc.), and elaborates ways in which these objects articulate such different temporal possibilities. For example, “fashion” enacts an eternally recurrent and capital time, whereas “arcades” represent wish images of the past that might be actualized into utopian promises of the future. My argument develops Benjamin's “objective” framing of temporality. In the Exposés specific and phenomenal things communicate temporalities specific to modernity. Objects not only communicate time but also enable the temporal experience of the modern subject. This reading challenges idealist interpretations of temporality grounded within an interiorizing subject. I do not argue that Benjamin privileges an objective temporal horizon “over” the subject but rather that he resituates dialectical possibilities of temporality in the engagement between subjects and commonplace objects.     

Collegiate Recovery Communities Programs: What Do We Know and What Do We Need to Know?

As the broad construct of recovery increasingly guides addiction services and policy, federal agencies have called for the expansion of peer-driven recovery support services. The high prevalence of substance use and abuse in colleges and universities in the United States constitutes a significant obstacle to pursuing an education for the unknown number of youths who have attained remission from substance use dependence. Collegiate recovery programs (CRPs) are an innovative and growing model of peer-driven recovery support delivered on college campuses. Although no systematic research has examined CRPs, available site-level records suggest encouraging outcomes: low relapse rates and above-average academic achievement. The number of CRPs nationwide is growing, but there is a noticeable lack of data on the model, its students, and their outcomes. We review the literature supporting the need for the expansion of CRPs, present information on the diversity of CRP services, and outline key areas where research is needed.