Batch sampling to improve power in a community trial. Experience from the Pawtucket Heart Health Program

Experiments involving large social units, such as schools, work sites, or whole cities, are commonly limited in statistical power because the number of randomized units is small, leaving few degrees of freedom for residual (between-unit) error. The authors describe a method for increasing residual degrees of freedom in a community experiment without substantially increasing cost or difficulty. In brief, they propose that the experimental units should be divided into random subsamples (batches). Batch sampling can improve statistical power if the community endpoint means are stable over time or if their temporal variation is comparable in period to the batch-sampling schedule. The authors demonstrate the theoretical advantages of the batch system and illustrate its use with data from the Pawtucket Heart Health Program, in which such a design was implemented.     

拉丁美洲的东亚移民

帝国主义通过扭曲遭受其影响的国家的经济,导致人口迁移与大量移民。19世纪,帝国主义势力渗透到远东的许多国家。在帝国主义与中国的贸易关系中,英国对茶叶的需求量相当大(其次是丝绸),但除了清政府需要的白银外,没有其他可交换的物品。为防止国库的耗尽和平衡贸易条款,英国商人于是寻求扩大中国的鸦片市场。东印度公司首先抢占了这个市场,然后鸦片贸易便被私人企业所垄断。在最大的经销商中,英国的贾丁与马西森公司位列其中(Hanes and Sanello,2002)。中国人的禁烟努力导致了1839—1842年和1856—1860年的两次鸦片战争,中国被迫割让香港给…     

Bounding Optimal Expected Revenues for Assortment Optimization under Mixtures of Multinomial Logits

We consider assortment problems under a mixture of multinomial logit models. There is a fixed revenue associated with each product. There are multiple customer types. Customers of different types choose according to different multinomial logit models whose parameters depend on the type of the customer. The goal is to find a set of products to offer so as to maximize the expected revenue obtained over all customer types. This assortment problem under the multinomial logit model with multiple customer types is NP‐complete. Although there are heuristics to find good assortments, it is difficult to verify the optimality gap of the heuristics. In this study, motivated by the difficulty of finding optimal solutions and verifying the optimality gap of heuristics, we develop an approach to construct an upper bound on the optimal expected revenue. Our approach can quickly provide upper bounds and these upper bounds can be quite tight. In our computational experiments, over a large set of randomly generated problem instances, the upper bounds provided by our approach deviate from the optimal expected revenues by 0.15% on average and by less than one percent in the worst case. By using our upper bounds, we are able to verify the optimality gaps of a greedy heuristic accurately, even when optimal solutions are not available.     

Comparison style, physical self-perceptions, and fitness among older women

This study examined the relationships between older women's comparison styles, physical self-perceptions, and functional fitness. Participants were community-dwelling women (N = 102, age 65-99) living in the mid-Atlantic region of the United States. Individuals were categorized as relying primarily on social comparisons, temporal comparisons, or a combination of both styles. Also of interest was whether individuals evaluated themselves positively or negatively when making comparisons. Participants who evaluated themselves positively as compared with others were found to have higher levels of physical self-perception. Analyses revealed that women who relied primarily on temporal comparisons had higher self-perceptions of their functional ability than those who relied on a combination of comparison styles. An avoidance of both temporal and social comparisons was also related to higher levels of physical self-perception.     

Female fertility history and mid-late-life health: Findings from China

China’s middle-aged and older women suffer from poorer health than men. Using national baseline data from the China Health and Retirement Longitudinal Study (CHARLS), a survey conducted from 2011 to 2012, this article applies logistic models to investigate the association between female fertility history (parity, early childbearing, late childbearing) and middle-aged and late-life health. We find that parity is related to the mid-late-life health of women. Women with four children or more are more likely to suffer from activities of daily living (ADL) impairment and poorer self-rated health than those with one to three children. Early childbearing is associated with ADL impairment; however, the correlation is mediated by socioeconomic status. Early childbearing is related to self-rated health in later life by an indirect-only mediation effect via educational attainment and personal income.     

Social firms: Building cross-sectoral partnerships to create employment opportunity and supportive workplaces for people with mental illness

A major barrier to employment for people with mental illness is limited access to supportive and non-discriminatory workplaces. Social firms are businesses committed to employing up to 50% of people with a disability or other disadvantage and to providing supportive work environments that benefit workers. Little research has been conducted to understand the features and social processes that support the vocational experiences of employees with mental health issues in social firms. Objective: This ethnographic study sought to explore the experiences of nine employees at one Australian social firm. Participants: Nine employees of a social firm, with and without mental illness. Methods: Study methods used included participant observation, interviewing and document analysis. Results and conclusions: The study highlights the complexity of running a socially-invested business, and the importance of cross-sectoral partnerships to support their operational success. Natural workplace supports, adequate training and support infrastructure and enabling participation in the business, were identified as important to creating a supportive workplace. Partnerships within the workplace and in support of the workplace are discussed. Future growth and development of partnerships are recommended to support the establishment of social firms.