The unified skew-t (SUT) is a flexible parametric multivariate distribution that accounts for skewness and heavy tails in the data. A few of its properties can be found scattered in the literature or in a parameterization that does not follow the original one for unified skew-normal (SUN) distributions, yet a systematic study is lacking. In this work, explicit properties of the multivariate SUT distribution are presented, such as its stochastic representations, moments, SUN-scale mixture representation, linear transformation, additivity, marginal distribution, canonical form, quadratic form, conditional distribution, change of latent dimensions, Mardia measures of multivariate skewness and kurtosis, and non-identifiability issue. These results are given in a parametrization that reduces to the original SUN distribution as a sub-model, hence facilitating the use of the SUT for applications. Several models based on the SUT distribution are provided for illustration.
翻译:统一偏t(SUT)分布是一种灵活的参数化多元分布,能够刻画数据中的偏态和厚尾特性。其部分性质虽散见于文献中,或存在于未遵循统一偏正态(SUN)分布原始参数化的其他参数化形式中,但尚缺乏系统性研究。本文系统阐述了多元SUT分布的显式性质,包括其随机表示、矩、SUN尺度混合表示、线性变换、可加性、边缘分布、规范形式、二次型、条件分布、隐维度变换、多元偏度与峰度的Mardia度量以及非可识别性问题。所有结论均基于一种能退化为原始SUN分布(作为子模型)的参数化形式,从而便于SUT分布的实际应用。文中还提供了若干基于SUT分布的模型作为示例。