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排序方式: 共有389条查询结果,搜索用时 15 毫秒
1.
Not having a variance estimator is a seriously weak point of a sampling design from a practical perspective. This paper provides unbiased variance estimators for several sampling designs based on inverse sampling, both with and without an adaptive component. It proposes a new design, which is called the general inverse sampling design, that avoids sampling an infeasibly large number of units. The paper provide estimators for this design as well as its adaptive modification. A simple artificial example is used to demonstrate the computations. The adaptive and non‐adaptive designs are compared using simulations based on real data sets. The results indicate that, for appropriate populations, the adaptive version can have a substantial variance reduction compared with the non‐adaptive version. Also, adaptive general inverse sampling with a limitation on the initial sample size has a greater variance reduction than without the limitation.  相似文献   
2.
Summary An increase in fish mortality due to fishing can theoretically change the growth and reproduction of fish populations from the viewpoint of adaptation. We address the issue of how an iteroparous fish should convert surplus energy into somatic growth and reproduction at each age under given conditions of mortality. A model of life history, which maximizes the net reproductive rate using the discrete maximum principle, is improved employing a new relationship between body weight and surplus energy which we have recently proposed. The model is applied to the North Sea plaicePleuronectes platessa, for which it has been reported that the average length of young fish had increased whereas that of old ones had decreased for some decades. Although the model cannot directly explain the former phenomenon, the two phenomena can be interpreted as a change in the optimal life history due mainly to an increase in mortality.  相似文献   
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"受事 施事 vp"型主谓谓语句的形成和使用受到句法、篇章的制约.在句法上有强调、突出受事主语和强调、突出补语成分的作用.在篇章中,受事主语有衔接连贯、对比和开启下文的作用,衔接连贯的受事主语能够使文气顺畅;对比的受事主语带有话题焦点的性质;开启下文的受事主语可以使主题统一;施事主语有对比强调和开启下文的作用,对比强调的施事主语带有对比焦点的性质;开启下文的施事主语起到主题统一的作用.  相似文献   
4.
Differences in patient characteristics, including age, sex, and race influence the safety and effectiveness of drugs, biologic products, and medical devices. Here we provide a summary of the topics discussed during the opening panel at the 2018 Johns Hopkins Center for Excellence in Regulatory Science and Innovation symposium on Assessing and Communicating Heterogeneity of Treatment Effects for Patient Subpopulations: Challenges and Opportunities. The goal of this session was to provide a brief overview of FDA-regulated therapeutics, including drugs, biologics and medical devices, and some of the major sources of heterogeneity of treatment effects (HTE) related to patient demographics, such as age, sex and race. The panel discussed the US Food and Drug Administration's role in reviewing and regulating drugs, devices, and biologic products and the challenges associated with ensuring that diverse patient populations benefit from these therapeutics. Ultimately, ensuring diverse demographic inclusion in clinical trials, and designing basic and clinical research studies to account for the intended patient population's age, sex, race, and genetic factors among other characteristics, will lead to better, safer therapies for diverse patient populations.  相似文献   
5.
Today, AIAN Elders are more actively engaged in their families and communities, encouraging the development of intergenerational programs, language and cultural revitalization, being stewards in research conducted in their communities, as well passing on their knowledge and experiences on how to live as healthy Native people. Elders have traditionally been quiet and observant of their environment, but the current and future cohorts of Elders are advocates, leaders, and culture bearers for their families and communities and they are now in positions of leadership. Western society acknowledges the value of traditional knowledge and AIAN Elders are viewed as exemplars of healthy aging and their lessons and experiences can be attributed to our own lives. This commentary highlights the paradigm shift in how society views older adults, specifically AIAN Elders and their role in health and wellbeing.  相似文献   
6.
The costs for rent and utilities account for the largest share of living expenses, yet these two critical dimensions of material hardship have seldom been examined concurrently in population-based studies. This paper employs multivariate statistical analysis using American Community Survey data to demonstrate the relative risk ratio of low-income renter-occupied households with children experiencing ‘rent burden', ‘energy insecurity', or a ‘double burden’ as opposed to no burden. Findings suggest that low-income households are more likely to experience these economic hardships in general but that specific groups are disproportionately burdened in different ways. For instance, whereas immigrants are more likely to experience rental burden, they are less likely to experience energy insecurity and are also spared from the double burden. In contrast, native-born African Americans are more likely than all other groups to experience the double burden. These results may be driven by the housing stock available to certain groups due to racial residential segregation, decisions regarding the quality of housing low-income householders are able to afford, as well as home-country values, such as modest living and energy conservation practices, among immigrant families. This paper also points to important policy gaps in safety net benefits related to housing and energy targeting low-income households.  相似文献   
7.
No abstract available for this article.  相似文献   
8.
This paper describes the findings of a survey of 1109 lesbians who attended the Women's Music Festival held in Michigan in carly August 1985. The primary objectives of the study were to document the incidence of domestic violence in a non-random sample of lesbian relationships; to identify and describe the types of domestic violence experienced and/or perpetrated; and to ascertain thc availability and accessibility of community helping resources to survivors and perpetrators after an abusive episode. Comparisons with domestic violence in heterosexual relationships are also made, followed by a discussion on the research and practice implications of the findings.  相似文献   
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