Mixture of Distributions in the Biparametric Exponential Family: A Bayesian Approach

In this article we propose mixture of distributions belonging to the biparametric exponential family, considering joint modeling of the mean and variance (or dispersion) parameters. As special cases we consider mixtures of normal and gamma distributions. A novel Bayesian methodology, using Markov Chain Monte Carlo (MCMC) methods, is proposed to obtain the posterior summaries of interest. We include simulations and real data examples to illustrate de performance of the proposal.     

A Review Essay on the Measurement of Child Well-Being

Research on indicators related to the state of child well-being is a growing field that has experienced several changes over time. The growing supply of data on children, as well as the need to facilitate conclusions and to track trends, has led researchers to develop a number of child well-being indexes. This paper critically reviews the most recent and relevant child well-being indexes, i.e., the Index of Child and Youth Well-Being in the United States, the Child Well-being Index for the European Union, the Microdata Child Well-being Index, and the Deprivation Index. The study focuses primarily on the contributions and innovations the indexes have brought to the field, making a critical assessment of the methods used in the construction of the indexes and identifying their main limitations.     

Does the presence of independent and female directors impact firm performance? A multi-country study of board diversity

This study empirically analyzes whether gender diversity enhances boards of directors’ independence and efficiency. Using data from 3,876 public firms in 47 countries and controlling for a wide set of corporate governance mechanisms, we find that firms with more female directors have higher firm performance by market (Tobin’s Q) and accounting (return on assets) measures. The results also suggest that external independent directors do not contribute to firm performance unless the board is gender diversified. These results hold with respect to different estimation models and robustness tests. Overall, our findings provide evidence that the female directors enhance boards of directors’ effectiveness. Finally, we find that firms that are concerned with board independence, and that firms in more complex environments are more likely to have gender-balanced boards.     

The Interaction between Negative Emotionality and Effortful Control in Early Social‐emotional Development

Interactions between reactive and regulatory dimensions of temperament may be particularly relevant to children's adjustment but are examined infrequently. This study investigated these interactions by examining effortful control as a moderator of the relations of fear and frustration reactivity to children's social competence, internalizing, and externalizing problems. Participants included 306 three‐year‐old children and their mothers. Children's effortful control was measured using observational measures, and reactivity was assessed with both observational and mother‐reported measures. Mothers reported on children's adjustment. Significant interactions indicated that children with higher mother‐reported fear or higher observed frustration and lower executive control showed higher externalizing problems whereas children with higher observed fear and higher delay ability demonstrated lower externalizing problems. These results highlight effortful control as a moderator of the relation between reactivity and adjustment, and may inform the development of interventions geared toward the management of specific negative affects.     

The entry of women in predominantly male professions: when training supports the search of alternative ways of organizing work time

Following a research carried out on the integration of women in professional areas predominantly for men, this paper intends to present and debate the project of a training course which aims the transformation of the organization of work schedules in order to improve the well-being of the workers involved. The conception of training courses with this type of objective involves the confrontation and debate between the "invested skills" of the trainers and the "constituted skills" of the trainees. But will this paradigm remain intact when applied to training courses permeated by the gender dimension? That is what one will try to realize with the effective implementation of a training course, whose reflection will allow, ultimately, to enrich our understanding on gender, work, health and training.     

Increasing College Access and Retention Rates of Youth in Foster Care: An Analysis of the Impact of 22 State Tuition Waiver Programs

Youth in foster care face educational disparities in terms of college access, retention, and graduation. To address this, 22 states have implemented tuition waiver programs targeting current and former foster youth. A comparative analysis was conducted of all 22 programs implemented since 2014. Similarities include student eligibility based on youth’s age upon foster care entry, university admission and time in care requirements. Differences include type of expenses covered, time limits on use, program oversight, and funding availability. No differences were found based on political party control, gubernatorial power, and state population composition. Recommendations for policy and practice reform are offered.     

A class of regression models for parallel and series systems with a random number of components

We extend the Weibull power series (WPS) class of distributions to the new class of extended Weibull power series (EWPS) class of distributions. The EWPS distributions are related to series and parallel systems with a random number of components, whereas the WPS distributions [Morais AL, Barreto-Souza W. A compound class of Weibull and power series distributions. Computational Statistics and Data Analysis. 2011;55:1410–1425] are related to series systems only. Unlike the WPS distributions, for which the Weibull is a limiting special case, the Weibull law is a particular case of the EWPS distributions. We prove that the distributions in this class are identifiable under a simple assumption. We also prove stochastic and hazard rate order results and highlight that the shapes of the EWPS distributions are markedly more flexible than the shapes of the WPS distributions. We define a regression model for the EWPS response random variable to model a scale parameter and its quantiles. We present the maximum likelihood estimator and prove its consistency and asymptotic normal distribution. Although series and parallel systems motivated the construction of this class, the EWPS distributions are suitable for modelling a wide range of positive data sets. To illustrate potential uses of this model, we apply it to a real data set on the tensile strength of coconut fibres and present a simple device for diagnostic purposes.     

Shewhart control charts for the scale parameter of a Weibull control variable with fixed and variable sampling intervals

In this paper, we are concerned with pure statistical Shewhart control charts for the scale parameter of the three-parameter Weibull control variable, where, and are the location, the scale and the shape parameters, respectively, with fixed (FSI) and variable (VSI) sampling intervals. The parameters and are assumed to be known. We consider two-sided, and lower and upper one-sided Shewhart control charts and their FSI and VSI versions . They jointly control the mean and the variance of the Weibull control variable X. The pivotal statistic of those control charts is the maximum-likelihood estimator of for the Nth random sample XN=(X1N,X2N,...,XnN) of the Weibull control variable X. The design and performance of these control charts are studied. Two criteria, i.e. 'comparability criterion' (or 'matched criterion') under control and 'primordial criterion', are imposed on their design. The performance of these control charts is measured using the function average time to signal. For the VSI versions, the constant which defines the partition of the 'continuation region' is obtained through the 'comparability criterion' under control. The monotonic behaviour of the function average time to signal in terms of the parameters (magnitude of the shift suff ered by the target value 0), and is studied. We show that the function average time to signal of all the control charts studied in this paper does not depend on the value of the parameter or on 0, and, under control, does not depend on the parameter, when Delta (the probability of a false alarm) and n (sample size) are fixed. All control charts satisfy the 'primordial criterion' and, for fixed, on average, they all (except the two-sided VSI, for which we were not able to ascertain proof) are quicker in detecting the shift as increases. We conjecture - and we are not contradicted by the numerical example considered - that the same is true for the two-sided VSI control chart. We prove that, under the average time to signal criterion, the VSI versions are always preferable to their FSI versions. In the case of one-sided control charts, under the 'comparability criterion', the VSI version is always preferable to the FSI version, and this advantage increases with and the extent of the shift. Our one-sided control charts perform better and have more powerful statistical properties than does our two-sided control chart. The numerical example where n=5,0=1,=0.5, 1.0, 2.0, and Delta=1/370.4 is presented for the two-sided, and the lower and upper one-sided control charts. These numerical results are presented in tables and in figures. The joint influence of the parameters and in the function average time to signal is illustrated.     

The relationship between sexual abuse and drug use: findings from Houston's Safer Choices 2 program

Self-report drug use data were collected from 282 female alternative school students surveyed through the Safer Choices 2 study in Houston, Texas. Data collection took place between October 2000 and March 2001 via audio-enabled laptop computers equipped with headphones. Logistic regression analyses indicated that sexual abuse history was significantly associated with lifetime use (OR = 1.9, p < or = 0.05). While the relationships tested in this study are exploratory, they provide evidence for an important connection between sexual abuse and substance use among female alternative school students.