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LOCAL INFLUENCE ASSESSMENT IN A MULTIVARIATE t-MODEL WITH RAO'S SIMPLE STRUCTURE 被引量:3
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作者 邹清明 张怀雄 《Acta Mathematica Scientia》 SCIE CSCD 2005年第1期179-192,共14页
The local influence analysis is an important problem in statistical inference and some models have been discussed in many literatures This paper deals with the problem of assessing local influences in a multivariate t... The local influence analysis is an important problem in statistical inference and some models have been discussed in many literatures This paper deals with the problem of assessing local influences in a multivariate t-model with Rao's simple struc-ture(RSS). Based on Cook's likelihood displacement, the effects of some minor perturbation on the statistical inference is assessed. As an application, a common covariance-weighted perturbation is thoroughly discussed. 展开更多
关键词 Multivariate t-model rao's simple structure ω-model likelihood displacement MLE
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ASSESSMENT OF LOCAL INFLUENCE IN A GROWTH CURVE MODEL WITH RAO'S SIMPLE COVARIANCE STRUCTURE 被引量:2
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作者 白鹏 《Acta Mathematica Scientia》 SCIE CSCD 1999年第S1期555-563,共9页
The present paper deals with the problem of assessing the local influence in a growth curve model with Rao's simple covariance structure. Based on the likelihood displacement,the curvature measure is employed to e... The present paper deals with the problem of assessing the local influence in a growth curve model with Rao's simple covariance structure. Based on the likelihood displacement,the curvature measure is employed to evaluate the effects of some minor perturbations on the statistical inference, thus leading to the large curvature direction, which is the most critical diagnostic statistic in the context of the local influence analysis. As an application, the common covariance-weighted perturbation scheme is thoroughly considered. 展开更多
关键词 Growth curve model rao's simple covariance structure w-model Likelihood displacement CURVATURE
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不同水盐梯度下功能多样性和功能冗余对荒漠植物群落稳定性的影响 被引量:19
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作者 王恒方 吕光辉 +1 位作者 周耀治 曹靖 《生态学报》 CAS CSCD 北大核心 2017年第23期7928-7937,共10页
功能多样性和功能冗余是物种多样性的两个组成部分,也是影响群落稳定性的两个重要因素。基于不同水盐梯度下植物功能多样性、功能冗余、物种多样性和群落稳定性及其相关关系的计算结果,分析功能多样性和功能冗余对群落稳定性的影响,结... 功能多样性和功能冗余是物种多样性的两个组成部分,也是影响群落稳定性的两个重要因素。基于不同水盐梯度下植物功能多样性、功能冗余、物种多样性和群落稳定性及其相关关系的计算结果,分析功能多样性和功能冗余对群落稳定性的影响,结果表明:(1)功能多样性、物种多样性和群落稳定性均表现为高水高盐和中水中盐群落显著高于低水低盐群落(P<0.05);(2)高水高盐群落,功能多样性与物种多样性的相关系数小于功能冗余与物种多样性的相关系数,且功能多样性与稳定性的相关系数也小于功能冗余与稳定性的相关系数,而中水中盐和低水低盐群落的相关系数则呈现相反的规律;(3)中水中盐和低水低盐群落的功能多样性的标准化偏回归系数均大于功能冗余的标准化偏回归系数;(4)典范对应分析中,土壤含水量可以解释总特征根的22.7%,而土壤含盐量仅可以解释总特征根的1.3%;(5)高水高盐群落的稳定比最接近20/80,稳定性最高;低水低盐群落远离20/80,稳定性最低。改进后的Godron稳定性测定方法与物种种群密度变异系数方法得出的结果相同。综上可知,功能多样性和功能冗余两者中与物种多样性关系更为密切者对群落稳定性的影响也越大,且两者均可提高群落稳定性,也就证明冗余假说在温带干旱荒漠区域的隐域性植物群落中是成立的;群落稳定性、功能多样性、功能冗余及物种多样性主要是受土壤含水量的影响,土壤含盐量对其影响较小。 展开更多
关键词 物种多样性 rao's指数 荒漠植物群落 冗余假说
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On some aspects of a bivariate alternative zero-inflated logarithmic series distribution
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作者 C.Satheesh Kumar A.Riyaz 《Statistical Theory and Related Fields》 CSCD 2023年第2期130-143,共14页
In this paper,we discuss some important aspects of the bivariate alternative zero inflated log-arithmic series distribution(BAZILSD)of which the marginals are the alternative zero-inflated logarithmic series ditributi... In this paper,we discuss some important aspects of the bivariate alternative zero inflated log-arithmic series distribution(BAZILSD)of which the marginals are the alternative zero-inflated logarithmic series ditributions of Kumar and Riyaz(2015.An alternative version of zero-inflated logarithmic series distribution and some of its applications.Journal of Statistical Computation and Simulation,85(6),1117-1127).We study some important properties of the distribution by deriving expressions for its probability mass function,factorial moments,conditional probabil-ity generating functions,and recursion formulae for its probilities,raw moments and factorial moments.The parameters of the BAZILSD are estimated by the method of maximum likelihood and certain test procedures are also considered.Further certain real-life data applications are cited for ilustrating the usefulness of the model.A simulation study is conducted for assessing the performance of the maximum likelihood estimators of the parameters of the BAZILSD. 展开更多
关键词 Factorial moments generalized lkeliood ratio test probability generating function rao's score test zero-inflated distributions
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