Control charts for generalized exponential distribution percentiles

The generalized exponential (GE) distribution, which was introduced by Mudholkar and Srivastava in 1993 Mudholkar, G. S., Srivastava, D. K. (1993). Exponentiated Weibull family for analyzing bathtub failure data. IEEE Transactions on Reliability 42:299–302. [Google Scholar], has been studied for various applications of lifetime modelings. In this article, five control charts, that comprise the Shewhart-type chart and four parametric bootstrap charts based on maximum likelihood estimation method, the moment estimation method, probability plot method, and least-square error method for the GE percentiles, are investigated. An extensive Monte Carlo simulation study is conducted to compare the performance among all five control charts in terms of average run length. Finally, an example is given for illustration.     

Race-Ethnicity and Health Trajectories: Tests of Three Hypotheses across Multiple Groups and Health Outcomes

Racial-ethnic disparities in static levels of health are well documented. Less is known about racial-ethnic differences in age trajectories of health. The few studies on this topic have examined only single health outcomes and focused on black-white disparities. This study extends prior research by using a life course perspective, panel data from the Health and Retirement Study, and multilevel growth curve models to investigate racial-ethnic differences in the trajectories of serious conditions and functional limitations among blacks, Mexican Americans, and whites. We test three hypotheses on the nature of racial-ethnic disparities in health across the life course (aging-as-leveler, persistent inequality, and cumulative disadvantage). Results controlling for mortality selection reveal that support for the hypotheses varies by health outcome, racial-ethnic group, and life stage. Controlling for childhood socioeconomic status, adult social and economic resources, and health behaviors reduces but does not eliminate racial-ethnic disparities in health trajectories.     

Is Executive Cognitive Function Associated with Youth Gambling?

Our objectives for this report were to identify trajectories of youth gambling behavior, and to examine their relation to executive cognitive function (ECF) and associated problem behaviors. Philadelphia school children, enrolled at ages 10–12 years (n = 387; 49% male), completed three annual assessments of risk behaviors, ECF, impulsivity, problem behaviors and demographics. Across ages 10–15 years, using methods from Nagin et al., two groups were identified: Early Gamblers (n = 111) initiated early and continued in later assessments, and Later Gamblers (n = 276) initiated at later ages and gambled less. Betting money on cards and sports were the most frequently reported gambling behaviors. Using gambling group as outcome, final backward selection logistic regression model showed Early Gamblers are more likely male (P = 0.001), report more active coping (P = 0.042), impulsive behaviors (P ≤ 0.008), and have friends who gamble (P = 0.001). Groups were similar in ECF, parental monitoring, marital status, SES, and race. Early Gamblers had higher incidence of problem behaviors and drug use (all P ≤ 0.006). Two gambling groups were identified in early adolescence with Early Gamblers showing higher levels of impulsivity and comorbid problems but similar levels of ECF compared to Late Gamblers. As more gambling groups are identified through later adolescence, ECF may emerge as a relevant precursor of problem gambling at this later time.     

Low Trait Self-Control in Problem Gamblers: Evidence from Self-Report and Behavioral Measures

Problems with self-control are seen as a key cause of problem gambling behavior. Yet, self-control is rarely studied directly in gambling studies. We demonstrated that self-report and behavioral measures (derived from the strength model of self-control) show lower trait self-control in problem gamblers. In Study 1, a sample of 2,208 undergraduate students from the University of Guelph, Canada (73% female, mean age?=?19?years, SD?=?4) completed a self-report measure of self-control strength. In Study 2, a sample of 296 University of Guelph students and staff (58% female, mean age?=?19?years, SD?=?2) completed multiple behavioral measures of self-control strength. Both studies demonstrated that, compared to lower-risk gamblers, higher-risk gamblers have relative trait self-control deficits.     

Trends in Children's Family Instability, 1995–2010

Using data from the 1995 and 2006–2010 National Survey of Family Growth, the authors' study examined children's family instability from birth to age 12, emphasizing variation by racial and ethnic group. Period and cohort estimates revealed little change in children's experiences of family transitions during the past decade. Family instability levels were comparable for White and Hispanic children, and this pattern persisted over time. However, there was an increase in family instability among Black children, reflecting growth in the share of children born to single mothers who eventually formed partnerships. Indeed, children born to single mothers in the more recent cohort experienced more family transitions, on average, than did the earlier cohort, but family instability for children born to cohabiting mothers remained unchanged. This study elucidates the various family life course trajectories children experience, revealing how these patterns differ depending on family context at birth and by racial and ethnic group.     

Negotiating the NGO/Social Movement Dichotomy: Evidence from Punjab,India

Non-Government Organisations (NGOs) and social movements are often juxtaposed as two distinct modes of action within civil society. While NGOs are seen as being linked to the interests of donors and being composed primarily of middle-class professionals, social movements are presented as a more authentic expression of grassroots perspectives. While academic literature compares and contrasts these two forms of organisation in the abstract, there has been comparatively little research exploring how civil society actors themselves conceptualise the NGO/social movement dichotomy and how this influences their strategic decision making. The Kheti Virasat Mission (KVM), working in the North Indian state of Punjab, is a useful case for exploring this issue. KVM is one of a growing number of groups working in the field of sustainable agriculture that has chosen to adopt a social movement model of organisation and distance itself from NGOs. The case helps illuminate how and why social movements differentiate themselves from NGOs and the challenges they face in doing so.     

Urban predator–prey association: coyote and deer distributions in the Chicago metropolitan area

We examined how predator or prey presence, as well as local and landscape factors, influence the distribution of coyotes (Canis latrans) and white-tailed deer (Odocoileus virginianus) in the Chicago metropolitan area. We collected data for 2 years at 93 study sites along 3 transects of urbanization using motion-triggered cameras. Our primary objective was to determine the relationship among coyote and deer spatial and temporal distribution, habitat characteristics, and human activity using multi-season patch occupancy models. Coyote occupancy was most strongly linked to rates of site visitation by humans and dogs, and was more likely farther from the urban center, with coyote colonization of sites inversely related to road density, housing density, and human and dog site visitation. Deer more frequently occupied sites with high canopy cover near water sources and colonized smaller sites with reduced housing density and human and dog presence. Expected predator–prey dynamics were altered in this highly urban system. Though we predicted deer would avoid coyotes on the landscape based on an “ecology of fear” framework, deer and coyote occupancy showed a strong positive association. We suggest that a scarcity of quality habitat in urban areas may cause the species to co-occupy habitat despite potential fawn predation. Modifying human foot traffic in green spaces may represent a useful tool for management and conservation of large urban mammals.     

Pubertal Timing and Adolescent Substance Initiation

We tested 3 competing hypotheses regarding the relation between pubertal timing and substance initiation in adolescence: the early timing, off-time, and stressful change hypotheses. We used longitudinal data from the Developmental Pathways Project (N = 521). Youth reported whether they had ever tried alcohol, tobacco, or marijuana at baseline, and then again at 6-, 12-, 18-, 24-, 36-, and 72-month follow-up interviews. We estimated interval censored parametric survival models and tested interactions between pubertal timing and gender and race variables. We found robust support for the early timing hypothesis, but no support for the off-time and the stressful change hypotheses.