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1.
2.
Consider the two linear regression models of Yij on Xij, namely Yij = βio + βil Xij + εij,j = 1,2,…,ni, i = 1,2, where εij are assumed to be normally distributed with zero mean and common unknown variance σ2. The estimated value of a mean of Y1 for a given value of X1 is made to depend on a preliminary test of significance of the hypothesis β11 = β21. The bias and the mean square error of the estimator for the conditional mean of Y1 are given. The relative efficiency of the estimator to the usual estimator is computed and is used to determine a proper choice of the significance level of the preliminary test.  相似文献   

3.
In this paper, a generalized ratio-cum-product estimator for estimating the ratio (product) of two population means using auxiliary information on two other variables is given of which the estimators by SINGH (1969) and SHAH and SHAH (1978) are particular cases. The estimator is regeneralized when the covariance between two auxiliary variables is known.  相似文献   

4.
Two linear functions for discriminating with qualitative variables (Fisher's linear discriminant function and the independence rule) are compared with the general multinomial procedure, a rule based on Lancaster's definition of higher order interactions and the quadratic discriminant function. The evaluation of these functions is carried out within Monte Carlo experiments. Various types of underlying distributions generated by a special algorithm are used.  相似文献   

5.
The behavior of Pearson's X2 test, the likelihood ratio test Y2 and the two of its derivatives, G2 and Gk2, the Freeman-Tukey test (FT) and the Cressie and Read test Statistic I(2/3) are examined in this study. Estimated attained α levels based on 1000 simulated samples when the approximating distribution is χk-12, are computed for these tests for the various values of k, n and seven null hypotheses. Results from estimated power computations indicate that none of the test statistics has a clear advantage over any others, and that the choice of which test to use must therefore rest mainly on the performances with regards to the attained α levels when the χ2 approximation is invoked. In this respect, the log-normal approximation proposed by Lawal and Upton (1980) is strongly recommended. This is closely followed by the I(2/3).  相似文献   

6.
Highly purified and biologically active [3H]tuftsin (specific activity 9 Ci/mmol) was synthesized and its binding to several types of human circulating blood cells was studied at 22°C. The binding to polymorphonuclear leukocytes and to monocytes was found to be specific, fast, saturable and reversible. Values for the dissociation constants (KD) were derived from equilibrium experiments and are 130 and 125 nM, respectively. The number of binding sites is approximately 50,000 and 100,000 per cell, respectively. Under the same experimental conditions lymphocytes exhibited only a threshold binding capacity for [3H]tuftsin whereas erythrocytes revealed no detectable binding.  相似文献   

7.
Effective conservation and management require reliable monitoring methods and estimates of abundance to prioritize human and financial investments. Camera trapping is a non-invasive sampling method allowing the use of capture–recapture (CR) models to estimate abundance while accounting for the difficulty of detecting individuals in the wild. We investigated the relative performance of standard closed CR models and spatially explicit CR models (SECR) that incorporate spatial information in the data. Using simulations, we considered 4 scenarios comparing low versus high detection probability and small versus large populations and contrasted abundance estimates obtained from both approaches. Standard CR and SECR models both provided minimally biased abundance estimates, but precision was improved when using SECR models. The associated confidence intervals also provided better coverage than their non-spatial counterpart. We concluded SECR models exhibit better statistical performance than standard closed CR models and allow for sound management strategies based on density maps of activity centers. To illustrate the comparison, we considered the Eurasian lynx (Lynx lynx) as a case study that provided the first abundance estimates of a local population in France. © 2012 The Wildlife Society.  相似文献   

8.
Some numerical results are presented for generalized ridge regression where the additive constants are based on the data. The adaptive estimator so obtained is compared with the least-squares estimator on the basis of mean square error (MSE). It is shown that the MSE of each component of the vector of ridge estimators may be as low as 47.1% of the variance of the corresponding component of the least squares vector or as high as 125.2%.  相似文献   

9.
Product method of estimation (MURTHY, 1964) using supplementary information on an auxiliary variable having high negative correlation with the main variable under our study, is well known. In this paper, we propose product-cum-difference method of estimation for the population total and the product of population parameters when supplementary information is available on two auxiliary variables. A comparison of product-cum-difference method of estimation with the usual product method of estimation using single auxiliary character and the estimators by SINGH (1965) for the estimation of product of population parameters has been made along with an empirical study.  相似文献   

10.
Using two-phase sampling mechanism, two alternative estimators in the presence of the available knowledge on second auxiliary variable z are considered, when the population mean of the main auxiliary variable × is unknown. The suggested estimators are found to be more eficient than the ratio-type and regression-type estimators suggested by KIREGYERA (1980, 1984).  相似文献   

11.
Two minimum mean square error estimators of heritability are proposed and compared with the conventional regression estimator with live data.  相似文献   

12.
Climate change is expected to have a significant effect on the first flowering date (FFD) in plants flowering in early spring. Prunus yedoensis Matsum is a good model plant for analyzing this effect. In this study, we used a degree day model to analyze the effect of air temperatures on the FFDs of P. yedoensis at Wuhan University from a long-time series from 1951 to 2012. First, the starting date (=7 February) is determined according to the lowest correlation coefficient between the FFD and the daily average accumulated degree days (ADD). Second, the base temperature (=−1.2°C) is determined according to the lowest root mean square error (RMSE) between the observed and predicted FFDs based on the mean of 62-year ADDs. Finally, based on this combination of starting date and base temperature, the daily average ADD of every year was calculated. Performing a linear fit of the daily average ADD to year, we find that there is an increasing trend that indicates climate warming from a biological climatic indicator. In addition, we find that the minimum annual temperature also has a significant effect on the FFD of P. yedoensis using the generalized additive model. This study provides a method for analyzing the climate change on the FFD in plants'' flowering in early spring.  相似文献   

13.
1980-2011年川东平行岭谷区农田土壤有机碳动态   总被引:4,自引:0,他引:4  
邵景安  惠辽辽  慈恩  谢德体 《生态学报》2014,34(15):4347-4360
选取重庆市垫江县为川东平行岭谷的典型区,使用1980第二次土壤普查和2011年实测土壤数据,基于土壤类型,运用通用SOC密度/储量计算法和逐步回归分析,对研究区1980—2011年0—20 cm农田SOC动态和动因进行分析,结果表明:(1)1980—2011年农田0—20 cm土层SOC密度/储量总体表现为略有增加态势,单位面积碳增量2307.63 kg C/hm2,碳增汇235945.83 t,增幅为10.74%,年均增长速率为72.11 kg C hm-2a-1;(2)丢碳、固碳和相对平衡面积比37.61∶49.03∶13.36,总体呈西部、西北部高于南部、东南部,更高于东北部和西南部的格局;(3)宏观上1980—2011年农田0—20 cm土层SOC密度/储量变化与土壤类型的分布及利用有很大关系,尤其是黄壤和紫色土在相异的质地本底和不同的扰动下,展现出相反的碳汇/源状态;(4)微观上SOC密度年均变化速率影响最大的因素是SOC密度初始值全N密度C/N比,且全N密度和C/N比拥有正向影响,SOC密度初始值则相反;⑸结果为川东平行岭谷区借助施加适当投入和合适的耕作与管理实践,有效管理农田表层SOC库提供科学依据。  相似文献   

14.
In this paper, by using the Lyapunov method, Itô’s differential formula and linear matrix inequality (LMI) approach, the global robust power-rate stability in mean square is discussed for genetic regulatory networks with unbounded time-varying delay, noise perturbations and parameter uncertainties. Sufficient conditions are given to ensure the robust power-rate stability (in mean square) of the genetic regulatory networks. Meanwhile, the criteria ensuring global power-rate stability in mean square are a byproduct of the criteria guaranteeing global robust power-rate stability in mean square. The obtained conditions are derived in terms of linear matrix inequalities (LMIs) which are easy to be verified via the LMI toolbox. An illustrative example is given to show the effectiveness of the obtained result.  相似文献   

15.
The use of ratio and product estimators, using auxiliary information, for estimating the mean of a finite population is well known. The efficiency of ratio estimator or product estimator is high depending on whether the auxiliary character is highly positively or negatively coorelated with the main character of interest. This paper proposes a product-type estimator which is more efficient than the usual ratio and product estimators in practical situations. We consider the case of double sampling from which the single sampling results may easily be derived.  相似文献   

16.
长三角城市群生态系统服务权衡强度时空演变及影响因素   总被引:1,自引:0,他引:1  
李成  赵洁  庄智程  顾思浩 《生态学报》2022,42(14):5708-5720
人类活动扰动加剧了长三角城市群生态系统结构演变,从而导致不同生态系统服务之间冲突加剧。明晰城市生态系统服务权衡强度及其影响因素对经济社会发展与生态保护的双赢具有重要意义。基于InVEST模型分析长三角城市群2005年、2019年碳储存、粮食生产、生境质量、产水量和氮输出量生态系统服务时空格局演变,并利用相关性分析、均方根误差指数和冗余分析方法,测度权衡强度并揭示权衡强度演变的关键影响因素。结果表明:粮食生产分别与碳储存、生境质量和产水量之间,以及氮输出量与生境质量和碳储存之间,碳储存与产水量之间呈现出显著的权衡关系;权衡强度空间异质性显著的粮食生产与碳储存,粮食生产与产水量的权衡强度高值主要集中在北部粮食主产区和南部山区。氮输出与碳储存、碳储存与产水量之间的高强度权衡关系主要位于南部地区。粮食生产与生境质量以及氮输出与生境质量的高强度权衡区域多集中在社会经济快速发展地区。长三角城市群生态系统服务权衡强度受多个因素共同作用,其主要影响因素包括坡度、林地覆盖率、农田覆盖率、降雨、气温、建设用地率等。  相似文献   

17.
The paper deals with the quadratic invariant estimators of the linear functions of variance components in mixed linear model. The estimator with locally minimal mean square error with respect to a parameter ? is derived. Under the condition of normality of the vector Y the theoretical values of MSE of several types of estimators are compared in two different mixed models; under a different types of distributions a simulation study is carried out for the behaviour of derived estimators.  相似文献   

18.
When stratified random sampling is used for the estimation of population mean, use of ‘Combined ratio estimator’ is well known. Some improved estimators for population mean are proposed which are better than ‘Combined ratio estimator’ and some other well known existing ones, from the point of view of bias and mean square error. An empirical illustration is given.  相似文献   

19.
Poger D  Fuchs JF  Nedev H  Ferrand M  Crouzy S 《FEBS letters》2005,579(24):5287-5292
Molecular dynamics simulations were performed on both apo and copper forms of the human copper chaperone, Hah1. Wild-type Hah1 and a methionine (M10) to serine mutant were investigated. We have evidenced the central role of residue M10 in stabilizing the hydrophobic core of Hah1 as well as the internal structure of the metal-binding site. When copper(I) is bound, the mobility of Hah1 is reduced whereas mutation of M10 implies a drastic increase of the mobility of apoHah1, stressing the importance of this highly conserved hydrophobic residue for copper sequestration by the apoprotein.  相似文献   

20.
The problem of estimation of, and statistical tests for, the relative risk (=α) from samples in which there is matching on covariates have been discussed by various authors (Cox, 1970; MANTEL and HAENSZEL, 1959) using the approach of conditional variates. This paper discusses log LR (likelihood ratio) tests of hypotheses concerning α, as based on one or more sets of matched samples. Approximate X2 tests are also developed for the hypotheses concerning α. An example is presented which illustrates the proposed tests of significance (Table 1).  相似文献   

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