Ordering results for series and parallel systems comprising heterogeneous exponentiated Weibull components

In this paper, we discuss the usual stochastic and reversed hazard rate orders between the series and parallel systems from two sets of independent heterogeneous exponentiated Weibull components. We also obtain the results concerning the convex transform orders between parallel systems and obtain necessary and sufficient conditions under which the dispersive and usual stochastic orders, and the right spread and increasing convex orders between the lifetimes of the two systems are equivalent. Finally, in the multiple-outlier exponentiated Weibull models, based on weak majorization and p-larger orders between the vectors of scale and shape parameters, some characterization results for comparing the lifetimes of parallel and series systems are also established, respectively. The results of this paper can be used in practical situations to find various bounds for the important aging characteristics of these systems.     

Confidence intervals based on the deviance statistic for the hyperparameters in state space models

The main objective of this work is to evaluate the performance of confidence intervals, built using the deviance statistic, for the hyperparameters of state space models. The first procedure is a marginal approximation to confidence regions, based on the likelihood test, and the second one is based on the signed root deviance profile. Those methods are computationally efficient and are not affected by problems such as intervals with limits outside the parameter space, which can be the case when the focus is on the variances of the errors. The procedures are compared to the usual approaches existing in the literature, which includes the method based on the asymptotic distribution of the maximum likelihood estimator, as well as bootstrap confidence intervals. The comparison is performed via a Monte Carlo study, in order to establish empirically the advantages and disadvantages of each method. The results show that the methods based on the deviance statistic possess a better coverage rate than the asymptotic and bootstrap procedures.     

A new aging concept derived from the increasing convex ordering

In this paper, a comparison between the life distribution of a new unit with that of a used unit in the increasing convex order is made leading to a new class of life distributions which we call “new better than used in convex ordering of second order”. This class includes as subclasses the NBU and the NBUC and is a subclass of the NBUCA class. Preservation properties under convolution, random maxima, mixing and formation of coherent structures are established. Stochastic comparisons of the excess lifetime when the inter-arrival times belong to the NBUC(2) class are developed. Some applications of Poisson shock models and a test of exponentiality against NBUC(2) alternative are presented.     

Extending Bayesian back-calculation to estimate age and time specific HIV incidence

Lifetime Data Analysis - CD4-based multi-state back-calculation methods are key for monitoring the HIV epidemic, providing estimates of HIV incidence and diagnosis rates by disentangling their...     

Social Welfare and Remittances to Older Adults in Two Caribbean Cities

This study explores the correlates of financial and material remittances to older adults in Havana and Bridgetown. These cities, both within countries at a very advanced stage of population ageing, have different institutional contexts for older adults. Data come from the 2000 Survey on Health, Well‐Being and Aging in Latin America and the Caribbean (SABE) of adults 60 years and older with children overseas, Havana (n = 461) and Bridgetown (n = 1,003), representing 342 and 531 families, respectively. Multivariate logistic regression analyses indicate that remittances to Havana were significantly associated with parents' and children's socio‐economic resources. Remittances to Bridgetown were associated with parents' sociodemographic characteristics and sibling's coresidence with parents. In both cities, remittances were positively associated with parents' support of their children. The findings suggest remittances are both a household survival strategy, which can reinforce socioeconomic inequality, and symbolic of social norms of family relations.     

The Importance of Racial Socialization: School‐Based Racial Discrimination and Racial Identity Among African American Adolescent Boys and Girls

This study examined various parental racial socialization messages as mediators between school‐based racial discrimination and racial identity formation over 4 years for African American boys (N = 639) and African American girls (N = 711). Findings indicated that school‐based racial discrimination was associated with racial identity beliefs. For African American boys, behavioral racial socialization messages mediated the relation between school‐based racial discrimination and racial centrality over time. Mediation also resulted for African American girls, but for a different set of race‐related messages (negative messages and racial barriers) and racial identity beliefs. The developmental significance of the findings and implications for future research are discussed.     

Interplay Between Sensation Seeking and Parental Rules in the Emergence of Heavy Episodic Drinking

This study examined the parallel mediational processes between sensation seeking and parental rules on alcohol, in the emergence of heavy episodic drinking (HED) in adolescents. Data were drawn from a U.K. clustered randomized control trial (control arm only, N ≈ 6,300, M_age at baseline = 12.5). Using parallel process latent growth curve analysis, stricter parental rules at baseline were found to be associated with greater declines in sensation seeking over time and a lower risk of HED at follow‐up (+33 months). Higher initial levels of sensation seeking predicted a faster relaxation of parental rules and a greater risk of HED. By maintaining strict rules about alcohol, parents may promote a positive reduction in sensation seeking and a lower risk of HED.     

Downsizing for downtown: limb lengths,toe lengths,and scale counts decrease with urbanization in western fence lizards (Sceloporus occidentalis)

Urban Ecosystems - Urbanization-induced habitat loss and alteration causes significant challenges for the survival of many species. Identifying how species respond to urbanization can yield...     

Level of choice in older women’s decisions to retire or continue working and associated well-being

Retirement is a complex life transition. Women’s retirement, like their work lives, may be further complicated, for example, by family or financial obligations; they may feel forced to retire or to continue working or feel they have the choice to do so. This study examines the role of voluntary versus involuntary retirement or continued work participation among retirement-age women; specifically, the relationships between choice, work status, and well-being. Compared to women forced to retire, women who chose retirement or continuing to work had higher levels of life satisfaction. Findings highlight the importance of examining retirement within the life course context.     

Child Obesity and the Interaction of Family and Neighborhood Socioeconomic Context

Population Research and Policy Review - The literature on neighborhoods and child obesity links contextual conditions to risk, assuming that if place matters, it matters in a similar way for...