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arXiv 1602.08558math.STstat.MEstat.TH
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具有适当先验的贝叶斯概率回归Gibbs抽样的收敛性质

Convergence properties of Gibbs samplers for Bayesian probit regression with proper priors

Saptarshi Chakraborty, Kshitij Khare

摘要:

贝叶斯概率回归模型(Albert和Chib(1993))是流行的,广泛用于二元回归。虽然在没有任何先验信息的情况下,回归系数的不适当的平坦先验是适当的选择,但是当先验信息可用时或者在系数的数量($p$)大于样本大小($n$)的现代高维设置中,适当的正态先验是期望的。对于这两种选择的先验,由此产生的后验密度是棘手的,数据Dugmentation(DA)马尔可夫链是用来产生近似样本的后验分布。建立这个DA马尔可夫链的几何遍历性是很重要的,因为它提供了理论保证构造标准误差的马尔可夫链为基础的后验量的估计。在本文中,我们首先表明,在正常的先验的情况下,DA马尔可夫链是几何遍历 * 的所有 * 选择的设计矩阵$X$,$n$和$p$(不像不适当的先验的情况下,其中$n \geq p$和另一个条件$X$后的适当性本身)。我们还得到了DA马尔可夫链是迹类的充分条件,即,相应算子的本征值是可求和的。特别是,这使我们能够得出结论,Haar PX-DA三明治算法(通过在DA算法的两个步骤之间插入一个廉价的额外步骤获得)在适当的意义上严格优于DA算法。

英文摘要:

The Bayesian probit regression model (Albert and Chib (1993)) is popular and widely used for binary regression. While the improper flat prior for the regression coefficients is an appropriate choice in the absence of any prior information, a proper normal prior is desirable when prior information is available or in modern high dimensional settings where the number of coefficients ($p$) is greater than the sample size ($n$). For both choices of priors, the resulting posterior density is intractable and a Data Dugmentation (DA) Markov chain is used to generate approximate samples from the posterior distribution. Establishing geometric ergodicity for this DA Markov chain is important as it provides theoretical guarantees for constructing standard errors for Markov chain based estimates of posterior quantities. In this paper, we first show that in case of proper normal priors, the DA Markov chain is geometrically ergodic *for all* choices of the design matrix $X$, $n$ and $p$ (unlike the improper prior case, where $n \geq p$ and another condition on $X$ are required for posterior propriety itself). We also derive sufficient conditions under which the DA Markov chain is trace-class, i.e., the eigenvalues of the corresponding operator are summable. In particular, this allows us to conclude that the Haar PX-DA sandwich algorithm (obtained by inserting an inexpensive extra step in between the two steps of the DA algorithm) is strictly better than the DA algorithm in an appropriate sense.

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