arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0708.0499math.STstat.TH
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混合对称分布的推断

Inference for mixtures of symmetric distributions

David R. Hunter, Shaoli Wang, Thomas P. Hettmansperger

摘要:

本文讨论了当混合组分是对称的且来自同一位置族时,有限混合模型的参数估计问题。我们把这些混合物称为半参数,因为除了对称性之外,没有对组分分布的参数形式进行额外的假设。由于对称分布的类是如此广泛,参数的可识别性是在这些混合的主要问题。我们提出了有限混合模型的可辨识性的概念,我们称之为k-可辨识性,其中k表示混合模型中组分的个数。当k=2或3时,给出了对称分量位置混合的k-可识别性的充分条件。本文提出了一种新的基于距离的方法来估计k-可辨识模型中的位置参数和混合参数,并证明了估计量的强相合性和渐近正态性.在L_2-距离的特殊情况下,我们证明了我们的估计推广了Hodges-Lehmann估计.我们讨论了这些程序的数值实现,以及经验估计的组件分布,在两个组件的情况下。与假设正态分量的极大似然估计相比,我们的方法在分量真正态的情况下产生稍高的标准误差估计,但在分量重尾的情况下显著优于正态方法.

英文摘要:

This article discusses the problem of estimation of parameters in finite mixtures when the mixture components are assumed to be symmetric and to come from the same location family. We refer to these mixtures as semi-parametric because no additional assumptions other than symmetry are made regarding the parametric form of the component distributions. Because the class of symmetric distributions is so broad, identifiability of parameters is a major issue in these mixtures. We develop a notion of identifiability of finite mixture models, which we call k-identifiability, where k denotes the number of components in the mixture. We give sufficient conditions for k-identifiability of location mixtures of symmetric components when k=2 or 3. We propose a novel distance-based method for estimating the (location and mixing) parameters from a k-identifiable model and establish the strong consistency and asymptotic normality of the estimator. In the specific case of L_2-distance, we show that our estimator generalizes the Hodges--Lehmann estimator. We discuss the numerical implementation of these procedures, along with an empirical estimate of the component distribution, in the two-component case. In comparisons with maximum likelihood estimation assuming normal components, our method produces somewhat higher standard error estimates in the case where the components are truly normal, but dramatically outperforms the normal method when the components are heavy-tailed.

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