This paper formulates and discusses a series of sequential decision problems of the following common structure: A decision alternative of multiple attributes‐that is, a job, an employee, or an investment alternative‐is to be selected within a certain fixed length of time. An unknown number of alternatives are presented sequentially, either deterministically or in a random manner. The decision maker can rank all the alternatives from best to worst without ties, and the decision to accept or reject an alternative is based solely on the relative ranks of those alternatives evaluated so far. The nonparametric sequential decision problem is first studied for a model involving a discrete time period and then generalized in terms of continuous time. Also considered is a variant of this problem involving a Bayesian estimation of (1) the uncertain probability of having an alternative at a given stage in the discrete‐time model and (2) the arrival rate of alternatives in the continuous‐time model. The optimal selection strategy that maximizes the probability of selecting the absolute best alternative is illustrated with the job search problem and the single‐machine job assignment problem. 相似文献
This study of the counties of South Carolina introduces a limited purpose, modifiable technology that is designed to reproduce
the rapid discovery strategy of the natural sciences. It uses factor analysis to identify types of communities and the threats
they face, and evaluates their success in dealing with these by comparisons based on age-adjusted mortality rates. The factor
analysis of mostly census indicators generated an Urbanization factor along with two measures of the interaction with the
environment, Growth and Poverty. Growth was expected to predict mortality negatively while Poverty should predict positively.
Regression analysis confirms both predictions but only for each race. That is, Growth predicted lower mortality, but only
for African-Americans. Poverty predicted higher mortality, but only for whites. These and other puzzling findings are explored,
illustrating the “rapid discovery” technology that is the central feature of this paper. 相似文献
ABSTRACT Domestic and family violence (DFV) is recognised as a health care priority. Women experiencing DFV use health services at a higher rate than the general population. Hospital social workers are an important component of a public hospital response to domestic and family violence but how prepared are they for this role? This research study explored the readiness of social workers in a Melbourne metropolitan hospital setting to respond to DFV. Results indicated that although the social workers had a knowledge base highly relevant for responding to DFV, many lacked specific knowledge of risk assessment, safety planning, legislative responsibilities, and referral pathways for support, including legal support. As a result, it was likely that they were not adequately responding, either by not recognising when they needed to, or with knowledge and confidence when they did. They also identified a range of organisational enablers, including policy, time, and safe conversation spaces. IMPLICATIONS
Hospital social workers have a central role to play in responding to domestic and family violence.
Hospital social workers need to be better prepared for domestic and family violence responses.
Social workers require ongoing training and organisational support including practice protocols and guidelines, and the provision of time and private, safe spaces for sensitive conversations to occur.
Universities should ensure that the role of hospital social workers is considered within curriculum addressing the area of domestic and family violence (DFV).
In the analysis of time‐to‐event data, competing risks occur when multiple event types are possible, and the occurrence of a competing event precludes the occurrence of the event of interest. In this situation, statistical methods that ignore competing risks can result in biased inference regarding the event of interest. We review the mechanisms that lead to bias and describe several statistical methods that have been proposed to avoid bias by formally accounting for competing risks in the analyses of the event of interest. Through simulation, we illustrate that Gray's test should be used in lieu of the logrank test for nonparametric hypothesis testing. We also compare the two most popular models for semiparametric modelling: the cause‐specific hazards (CSH) model and Fine‐Gray (F‐G) model. We explain how to interpret estimates obtained from each model and identify conditions under which the estimates of the hazard ratio and subhazard ratio differ numerically. Finally, we evaluate several model diagnostic methods with respect to their sensitivity to detect lack of fit when the CSH model holds, but the F‐G model is misspecified and vice versa. Our results illustrate that adequacy of model fit can strongly impact the validity of statistical inference. We recommend analysts incorporate a model diagnostic procedure and contingency to explore other appropriate models when designing trials in which competing risks are anticipated. 相似文献
VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - Philanthropic endeavors are a form of institutionalized collective action that enhances a community’s capacity to... 相似文献
We examined the relationship among perceived parental psychological control (PPC), self‐concept, and empathy, from adolescence to emerging adulthood. Child Development Project longitudinal data analyses indicate that, when adolescents notice PPC at age 13, they have poor self‐concept (less competence) at age 16, and they show less empathic concern (EC) toward others at age 24. The indirect effects of self‐concept at age 16 are significant for EC, but not for perspective taking (PT). Moreover, perceived PPC at age 13 does not directly predict their EC at age 24, but it does their PT at age 24, and these results were found regardless of the gender of the parents and adolescents. Our results shed light on poor self‐concept in adolescence as a mechanism by which PPC impairs healthy emotional development from adolescence to emerging adulthood. 相似文献
Urban Ecosystems - Gardens have effects on the local ecology as well as on the wellbeing of the gardener, but few studies have attempted to study gardens using both ecological and social outcome... 相似文献
Urban community gardens are potentially important sites for urban pollinator conservation because of their high density, diversity of flowering plants, and low pesticide use (relative to agricultural spaces). Selective planting of attractive crop plants is a simple and cost-effective strategy for attracting flower visitors to urban green spaces, however, there is limited empirical data about which plants are most attractive. Here, we identified key plant species that were important for supporting flower visitors using a network-based approach that combined metrics of flower visitor abundance and diversity on different crop species. We included a metric of ‘popularity’ which assessed how frequently a particular plant appeared within community gardens. We also determined the impact of garden characteristics such as size, flower species richness, and flower species density on the abundance and diversity of flower visitors. Two plant species, Brassica rapa and Ocimum basilicum were identified as being particularly important species for supporting flower visitor populations. Flower species richness had a strong positive effect on both the abundance and diversity of flower visitors. We suggest that gardeners can maximise the conservation value of their gardens by planting a wide variety of flowering plants including attractive plants such as B. rapa and O. basilicum.