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201.
When sample observations are expensive or difficult to obtain, ranked set sampling is known to be an efficient method for estimating the population mean, and in particular to improve on the sample mean estimator. Using best linear unbiased estimators, this paper considers the simple linear regression model with replicated observations. Use of a form of ranked set sampling is shown to be markedly more efficient for normal data when compared with the traditional simple linear regression estimators. 相似文献
202.
Benjamin Felzer Preston Heard 《Journal of the American Water Resources Association》1999,35(6):1327-1339
ABSTRACT: Two general circulation models (GCMs) used in the U.S. national assessment of the potential consequences of climate variability and change (CGCM1 and HadCM2) show a large increase in precipitation in the future over the southwestern U.S., particularly during winter. This precipitation increase is an extension of a larger region of increased precipitation in the Pacific Ocean off the west coast of North America that is associated with a deepened and southward-shifted Aleutian Low, a weaker subtropical high, and warmer sea surface temperatures (SSTs). The models differ in their simulation of precipitation anomalies over the southeastern U.S., with CGCM1 showing drier conditions and HadCM2 showing wetter conditions in the future. While both models show decreased frequency of Atlantic storms, consistent with decreased meridional and land/sea temperature gradients, the more coastal position of the storm track in CGCM1 results in less precipitation than modern along the eastern seaboard of the U.S. During summer, differences in land surface models within the two GCMs sometimes lead to differences in soil moisture that feed back to the precipitation over land due to available moisture. 相似文献
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本文在山西省排污权交易工作现有交易机制、政策设计与实践成果的基础上,分析现有排污权交易实施过程中存在的主要问题,并结合"十三五"时期国家对排污权交易工作的总体要求,提出山西省排污交易体系的改进设计建议。通过改进排污权初始分配方式和排污权交易模式,制定活跃排污权交易市场的相关政策,强化市场与政府的对接,探索山西省地方立法,扩展山西省排污权交易管理平台等,逐步完善交易制度建设、监管体系建设、信息统计体系建设,深化排污权交易支持下的山西省总量减排及环境监管能力建设,构建管理规范、交易顺畅的排污指标交易市场,支持排污权交易工作在山西省的全面推广与实施。 相似文献
205.
Estimation of Catchment Nutrient Loads in New Zealand Using Monthly Water Quality Monitoring Data
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T.H. Snelder R.W. McDowell C.E. Fraser 《Journal of the American Water Resources Association》2017,53(1):158-178
Causes of variation between loads estimated using alternative calculation methods and their repeatability were investigated using 20 years of daily flow and monthly concentration samples for 77 rivers in New Zealand. Loads of dissolved and total nitrogen and phosphorus were calculated using the Ratio, L5, and L7 methods. Estimates of loads and their precision associated with short‐term records of 5, 10, and 15 years were simulated by subsampling. The representativeness of the short‐term loads was quantified as the standard deviation of the 20 realizations. The L7 method generally produced more realistic loads with the highest precision and representativeness. Differences between load estimates were shown to be associated with poor agreement between the data and the underlying model. The best method was shown to depend on the match between the model and functional and distributional characteristics of the data, rather than on the contaminant. Short‐term load estimates poorly represented the long‐term load estimate, and deviations frequently exceeded estimated imprecision. The results highlight there is no single preferred load calculation method, the inadvisability of “unsupervised” load estimation and the importance of inspecting concentration‐flow, unit load‐flow plots and regression residuals. Regulatory authorities should be aware that the precision of loads estimated from monthly data are likely to be “optimistic” with respect to the actual repeatability of load estimates. 相似文献
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Korie S. Clark S.J Perry J.N Mugglestone M. A. Bartlett P .W. Marshall E. J . P. Mann J. A. 《Environmental and Ecological Statistics》1998,5(4):317-344
The spatial pattern of organisms may be used to characterize their dispersal, quantify spread or estimate the point of introduction of an alien species. Their distribution may be represented by maps of individuals, or by counts or by presence/absence at known positions within a sampled area. The problems and relative merits of these different forms of data for spatial inference are discussed. Three datasets concerning dispersal from a single focus are analyzed: counts of aphids, Rhopalosiphum padi and Sitobion avenae, on barley plants, Hordeum vulgare, grown in experi- mental trays; mapped locations of couch grass, Elymus repens, tillers within plots of a field experiment; locations of sightings of the lupin aphid, Macrosiphum albifrons, as it invaded Great Britain between 1981 and 1984. A method for generating maps from counts is proposed to overcome problems caused by recording imprecision. Several statistics are used to quantify dispersal and spatial pattern in the experimental data and together provide a clear picture of the spatial pattern observed; they enabled several effects of the experimental treatments to be identified. The value of the statistics are compared. Estimates of the source of the lupin aphid invasion are obtained using the backtracking methods of Perry (1995b) and do not contradict previous suggestions. 相似文献
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图书馆的读者借阅情况可反应出学生的学风及图书馆文献资源的适用情况,因此对流通记录的统计工作是图书馆的一项重要工作.通过对我馆图书馆管理系统软件后台数据的进一步分析,得出了读者到馆人次、人数及借阅图书类别等项目的统计数据,了解我院学生的图书借阅行为的概况,并进而分析图书馆在文献资源建设及图书馆服务方面存在的问题及并提出相应的解决方案. 相似文献
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