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261.
Markus Neuhäuser 《Environmental and Ecological Statistics》2004,11(3):295-304
In behavioral ecology the overall sex ratio in a population of birds is often tested to see if it differs from a 50/50 ratio. In recent publications the binomial test or the 2 test are carried out although the sexes of chicks within the same nest may not be independent. The lack of independence occurs since female birds can adjust the sex ratio in an adaptive way as demonstrated in recent studies. In order to take dependence into consideration the Wilcoxon signed rank test based on the within-brood differences between the proportions of sons and daughters was performed in a study investigating great tit hatchling sex ratios. We compare this test with a test based on an optimally weighted estimator recently proposed for medical studies with clustered binary data. According to our simulation results, this novel test is more powerful than the Wilcoxon signed rank test and should be used for the analysis of avian sex ratios. The methods are illustrated with real data from the great reed warbler. 相似文献
262.
W. Urfer F. H. Schwarzenbach J. Kötting P. Müller 《Environmental and Ecological Statistics》1994,1(3):171-192
This interdisciplinary research on forest ecosystems begins with some characteristics of ecosystems which are the basis for the derivation of statistical models for the development and vitality of trees. Several ecological problems which could be solved by longitudinal studies are mentioned. Statistical methods for the evaluation of the crowns of spruce trees (Picea abies Karst) in three permanent observation plots in Switzerland are described. In particular, the time-dependent proportional odds model and a transitional model are used. Through application of these multistate models the data give information on the dependence of an ordered categorical response variable on covariates characterizing the ecosystem. The response variable is observed through infrared aerial photographs. This monitoring system gives insight into the dynamic behaviour of the forest ecosystem. The need for more eco-systematically motivated statistical research using longitudinal studies is identified. 相似文献
263.
拟面积多波长数据线性双组合解析萘,1—萘酚和2—萘酚同步荧光光谱的研究 总被引:2,自引:0,他引:2
本文研究了Δλ(λem-λex)为130nm和PH12.0条件下,萘、1-萘粉和2-萘酚混合物的同步荧光光谱,获三者同步荧光峰信息,且萘被完全分辨,另外,提出用拟面积多波长线性双组合计算解析重叠的1-萘酚和2-萘酚同步荧光光谱,解析结果的精密度、组份间浓度比范围均较多波长线性回归、双峰增配平和一阶导数解析混合物同步荧光光谱结果为优。 相似文献
264.
Laboratory analyses in a variety of contexts may result in left- and interval-censored measurements. We develop and evaluate a maximum likelihood approach to linear regression analysis in this setting and compare this approach to commonly used simple substitution methods. We explore via simulation the impact on bias and power of censoring fraction and sample size in a range of settings. The maximum likelihood approach represents only a moderate increase in power, but we show that the bias in substitution estimates may be substantial. 相似文献
265.
A geo-referenced data set of 12 228 first-time blood lead screening values for Syracuse, NY, children was established for the 4-year period 1992–1996. Soil lead values were measured in a 600 m by 600 m tessellation grid covering the city. The two data sets were merged for evaluation of relationships between them. Strong seasonal variation in blood lead levels suggests the importance of contaminated soils as an exposure source. When the data were aggregated at a large geographic scale (3 km2), a logarithmic model showed an R2 of > 0.65 for the regression of geometric mean blood lead on median soil lead values. Results showed a striking similarity to those obtained by Mielke et al. (1999) for a study in New Orleans, LA, USA. 相似文献
266.
Ordered parameter problems arise in a wide variety of real world situations and are dealt with extensively in the literature. Traditional frequentist methods for dealing with these problems are rather complicated theoretically, especially when sample sizes are small. Bayesian methods are not widely used because high dimensional numerical integration is often required. However, Markov chain Monte Carlo methods provide alternatives to such numerical integration and also deal with ordered parameter problems in a straightforward manner. Little is known about the situation where functions of parameters are ordered. Such problems may seem to be of little practical concern initially, but one can readily see their importance in situations where ordering is placed on the means and variances of several normal or Gamma populations. For the Gamma distribution we will present real examples where we will analyze monthly precipitation data from San Francisco, California and Oakland Mills, Iowa. For the San Francisco data we will simultaneously order both monthly precipitation means and variances. For the Iowa data we will place ordering on seasonal average while still estimating monthly means. Our results show that we would obtain sharper, more accurate inference when order restrictions are employed. 相似文献
267.
David Gerard 《Resources Policy》1998,24(4):251-264
This paper applies a property rights framework to federal mineral lands in the western United States from the enactment of the Mining Law in 1872 until the enactment of the Mineral Leasing Act for fossil fuels in 1920. There are two principal findings. First, the Mining Law appears to have been an effective means for assigning rights to mineral stocks on public lands (at least through 1920). This conclusion is supported by evidence from claim disputes in the West. Second, the impetus for the Mineral Leasing Act did not derive from the different physical characteristics of hardrock minerals and petroleum. The relevance of these conclusions to contemporary mineral policy is also discussed. 相似文献
268.
在环境地学研究中应用GIS急需解决的问题分析 总被引:4,自引:0,他引:4
地理信息系统已经成为环境地学的常用工具,但主要被用来存储和显示地图,没有发挥其应有的功能。本文认为多源空间数据集成、空间数据分析和挖掘队及模型集成等是其中三个最主要问题。多源环境数据集成是基础,空间分析是连接多源数据集成与模型集成的桥梁和纽带,数据通过这个桥梁传输给模型,模型对环境系统进行模拟和仿真。这些问题的解决有利于更好地在环境地学中应用地理信息系统。 相似文献
269.
本文介绍了一种新研制的磁化率仪,它可测定自然界中大多数物质(良导体除外)的初始磁化率,特别适合于岩石的磁化率及其各向异性(AMS)测量。仪器工作磁场300A/m,频率920Hz,样机总磁化率测量灵敏度达到 2×10~(-12)m~3,读数采用数字显示方式并具有自动锁定功能。与计算机的联机采用了标准EIARS-232C串行接口,因此具有良好的通用性。在软件的控制下,计算机可自动完成测量数据的采集、计算处理、座标转换以及成图或存贮等工作,AMS参数的测量效率得到很大提高。 相似文献
270.