伊顿马尔可夫链何时不可约?
When is Eaton's Markov chain irreducible?
摘要:
考虑一个参数统计模型$P(\mathrm{d}x|θ)$和一个不适当的先验分布$ν(\mathrm{d}θ)$,它们一起产生一个(适当的)正式的后验分布$Q(\mathrm{d}θ|x)$。如果$θ$的每一个有界函数的广义Bayes估计在平方误差损失下是可容许的,则称先验是强可容许的。伊顿[安。20(1992)1147- 1179]已经证明$ν$强容许性的充分条件是其转移函数为$R(θ,\mathrm{d}η)=\int Q(\mathrm{d}η|x)P(\mathrm {d}x|θ)$的马尔可夫链的局部复发。当与$R$有关的马尔可夫链不可约时,这个结果及其推广的应用往往大大简化。然而,建立不可还原性可能很困难。本文给出了一般状态空间马氏链不可约性的一个刻画,并利用这个刻画给出了Eaton马尔可夫链不可约性的一个易于检验充要条件.要检查这种情况,只需简单检查$P$和$ν$。通过两个例子说明了主要结果的应用。
英文摘要:
Consider a parametric statistical model $P(\mathrm{d}x|θ)$ and an improper prior distribution $ν(\mathrm{d}θ)$ that together yield a (proper) formal posterior distribution $Q(\mathrm{d}θ|x)$. The prior is called strongly admissible if the generalized Bayes estimator of every bounded function of $θ$ is admissible under squared error loss. Eaton [Ann. Statist. 20 (1992) 1147--1179] has shown that a sufficient condition for strong admissibility of $ν$ is the local recurrence of the Markov chain whose transition function is $R(θ,\mathrm{d}η)=\int Q(\mathrm{d}η|x)P(\mathrm {d}x|θ)$. Applications of this result and its extensions are often greatly simplified when the Markov chain associated with $R$ is irreducible. However, establishing irreducibility can be difficult. In this paper, we provide a characterization of irreducibility for general state space Markov chains and use this characterization to develop an easily checked, necessary and sufficient condition for irreducibility of Eaton's Markov chain. All that is required to check this condition is a simple examination of $P$ and $ν$. Application of the main result is illustrated using two examples.
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