Non-parametric regression on compositional covariates using Bayesian P-splines

Methods to perform regression on compositional covariates have recently been proposed using isometric log-ratios (ilr) representation of compositional parts. This approach consists of first applying standard regression on ilr coordinates and second, transforming the estimated ilr coefficients into their contrast log-ratio counterparts. This gives easy-to-interpret parameters indicating the relative effect of each compositional part. In this work we present an extension of this framework, where compositional covariate effects are allowed to be smooth in the ilr domain. This is achieved by fitting a smooth function over the multidimensional ilr space, using Bayesian P-splines. Smoothness is achieved by assuming random walk priors on spline coefficients in a hierarchical Bayesian framework. The proposed methodology is applied to spatial data from an ecological survey on a gypsum outcrop located in the Emilia Romagna Region, Italy.     

A Historical Perspective on High School Students’ Paid Employment and Its Association with High School Dropout

Discussions about the role of paid employment in high school students’ lives usually involve untested assumptions about historical trends in the frequency, intensity, and selective nature of students’ employment behaviors. Using several nationally representative data sources, we find few changes in rates of employment or hours worked per week among adolescents since 1940 or among students since 1980. We observe important changes in recent decades in racial/ethnic and gender differences in employment and intensive employment. Finally, we observe that the relationship between students’ intensive employment and high school completion has been stable and persistently significant since the late 1960s.

Aggressive behaviour in adolescence: Links with self‐esteem and parental emotional availability

Aggressive behaviours during adolescence may be predictive of later conduct disorders, hence it is important to early detect their signals and deepen the study of their possible risk factors. In order to address these issues, our study pursued two main objectives: to evaluate the psychometric properties of the Italian adaptation of the Aggression Questionnaire Short‐Form (AQ‐SF), a form never previously used among Italian adolescents; and to investigate the relation among aggressiveness, emotional relationship with both parents and self‐esteem in a sample of adolescents. Our results highlighted that psychometric properties of the Italian AQ‐SF are satisfactory and encourage a wider use of this tool; in addition, we found that self‐esteem plays a mediation role between parental emotional availability and aggression. Prevention efforts should focus on improving the relationship with both parents and strengthening adolescent's self‐esteem.