نتایج جستجو برای: representative samples
تعداد نتایج: 500113 فیلتر نتایج به سال:
BACKGROUND Suicide is a problem of worldwide concern and research on possible protective factors is needed. We explored the role of social support as one such factor. Specifically, we hypothesized that increased social support would be associated with decreased likelihood of a lifetime suicide attempt in two nationally representative samples as well as a high-risk subsample. METHODS We analyz...
During the last two decades, laboratory experiments have come into increasing prominence and constitute a popular method of research to examine behavioral outcomes and social preferences. However, it has been debated whether results from these experiments can be extrapolated to the real world and whether, for example, sample selection into the experiment might constitute a major shortcoming of ...
BACKGROUND Clostridium difficile and Clostridium perfringens are commonly associated with colitis in equids, but healthy carriers exist. Scarce information is available on the prevalence of Clostridium spp. in gastrointestinal compartments other than faeces in healthy horses, and it is unknown whether faecal samples are representative of proximal compartments. The objectives were to investigate...
Abstract. This paper is concerned with the summarization of a set of categorical sequences. More specifically, the problem studied is the determination of the smallest possible number of representative sequences that ensure a given coverage of the whole set, i.e. that have together a given percentage of sequences in their neighbourhood. The proposed heuristic for extracting the representative s...
We present a fast and flexible program for clustering large protein databases at different sequence identity levels. It takes less than 2 h for the all-against-all sequence comparison and clustering of the non-redundant protein database of over 560,000 sequences on a high-end PC. The output database, including only the representative sequences, can be used for more efficient and sensitive datab...
BACKGROUND Recruiting large and representative samples of adolescent and young adult (AYA) cancer survivors is important for gaining accurate data regarding the prevalence of unmet needs in this population. This study aimed to describe recruitment rates for AYAs recruited through a cancer registry with particular focus on: active clinician consent protocols, reasons for clinicians not providing...
PURPOSE Social capital and social attachment theories of substance use argue that positive bonds to society and the conventional values they promote deter adolescents from substance use. Using nationally representative samples of U.S. high school seniors, we hypothesized that adolescents' community attachments, measured by social trust, social responsibility, and religiosity, would be negativel...
OBJECTIVES Free prescription drug samples are used widely in the United States. We sought to examine characteristics of free drug sample recipients nationwide. METHODS We analyzed data on 32681 US residents from the 2003 Medical Expenditure Panel Survey (MEPS), a nationally representative survey. RESULTS In 2003, 12% of Americans received at least 1 free sample. A higher proportion of perso...
It is difficult for learning models to achieve high classification performances with imbalanced data sets, because with imbalanced data sets, when one of the classes is much larger than the others, most machine learning and data mining classifiers are overly influenced by the larger classes and ignore the smaller ones. As a result, the classification algorithms often have poor learning performa...
As implementation of the Ballast Water Convention draws nearer a major challenge is the development of protocols which accurately assess compliance with the D-2 Standard. Many factors affect the accuracy of assessment: e.g. large volume of ballast water, the shape, size and number of ballast tanks and the heterogeneous distribution of organisms within tanks. These factors hinder efforts to obta...
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