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Use of Hotelling's T^2: Outlier Diagnostics in Mixtures

机译:使用Hotelling的T ^ 2:在混合物中的异常诊断

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Given Gaussian observation vectors $[seqcl{BY}{n}]$ having a common mean and dispersion matrix, a pervading issue is to identify shifted observations of type ${BYi!o!BYi!+!deli}.$ Conventional usage enjoins Hotelling's $Tisq$ diagnostics, derived and applied under the mutual independence of $[seqcl{BY}{n}]$. Independence often fails, yet the need to identify outliers nonetheless persists. Accordingly, the present study reexamines $Tisq$ under dependencies to include equicorrelations and more general matrices. Such dependencies are found in the analysis of calibrated vector measurements and elsewhere. In addition, mixtures of these distributions having star--shaped contours arise on occasion in practice. Nonetheless, the $Tisq$ diagnostics are shown to remain exact in level and power for all such mixtures. Moreover, further matrix distributions, not necessarily having finite moments, are seen to generalize $n$--dimensional spherical symmetry to include non--Gaussian matrices of order $(n!imes!k)$ supporting $Tisq.$ For these the use of $Tisq$ remains exact in level. These findings serve to expand considerably the range of applicability of $Tisq$ in practice, to include matrix Cauchy and other heavy tailed distributions intrinsic to econometric and other studies. Case studies serve to illuminate the methodology.
机译:给定高斯观察向量$ [ seqcl { by} {n}] $具有常见的均值和色散矩阵,遍布遗传问题是识别$ { byi ! to ! byi 的转移观察。 + ! bdeli }。$常规使用禁止Hotelling的$ tisq $诊断,衍生和应用于$ [ seqcl { by} {n}] $的相互独立性。独立性经常失败,但仍然需要识别异常值仍然存在。因此,本研究重新审视了依赖性的$ TISQ $,以包括等式和更通用的矩阵。在校准的矢量测量和其他地方的分析中发现了这种依赖性。此外,在实践中偶尔出现具有星形轮廓的这些分布的混合物。尽管如此,可以显示$ TISQ $诊断,以确保所有此类混合物的级别和电源保持精确。此外,还观察到进一步的矩阵分布,不一定具有有限的时刻,以概括N $维球形对称,以包括非高斯$(n ! times k)$支持$ tisq的矩阵。 $于这些,使用$ TISQ $仍然是精确的级别。这些调查结果有助于扩展$ TISQ $的适用范围,包括矩阵CAUCHY和其他重尾分布的经济学和其他研究。案例研究有助于阐明方法。

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