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arXiv 1303.7152math.STstat.TH
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反集中和诚实,自适应置信带

Anti-concentration and honest, adaptive confidence bands

Victor Chernozhukov, Denis Chetverikov, Kengo Kato

摘要:

非参数密度(和其他函数)的均匀置信带的现代构造通常依赖于经典的Smirnov-Bickel-Rosenblatt(SBR)条件;例如,参见Giné和Nickl [Probab.理论相关领域143(2009)569-596]。该条件要求学生化经验过程的上确界存在极值型极限分布(等价地,对于具有与学生化经验过程相同的协方差函数的高斯过程的上确界)。本文的主要贡献是消除了对这一经典条件的需要。我们证明了一个相当弱的充分条件来自近似高斯过程的上确界的反集中属性,我们推导出一个不等式,导致这样的属性可分高斯过程。我们把这个新条件称为广义SBR条件。我们的新结果表明,上确界不会太快地集中在任何值周围。然后,我们应用这一结果,推导出高斯乘数的自举过程,为非参数密度估计构建诚实的置信带(这一结果也可以应用于其他非参数问题)。我们的方法的一个重要优点是,它适用于一般情况下,即使在极限分布的上确界的学生化经验过程不存在(或未知)。这是特别重要的问题,分辨率水平或其他调谐参数已被选择在一个数据驱动的方式,这是需要自适应的置信带的建设。最后,独立的兴趣是我们引入了一个新的,实用的版本的Lepski的方法,它计算的最佳,非保守的分辨率水平通过高斯乘数自举方法。

英文摘要:

Modern construction of uniform confidence bands for nonparametric densities (and other functions) often relies on the classical Smirnov-Bickel-Rosenblatt (SBR) condition; see, for example, Giné and Nickl [Probab. Theory Related Fields 143 (2009) 569-596]. This condition requires the existence of a limit distribution of an extreme value type for the supremum of a studentized empirical process (equivalently, for the supremum of a Gaussian process with the same covariance function as that of the studentized empirical process). The principal contribution of this paper is to remove the need for this classical condition. We show that a considerably weaker sufficient condition is derived from an anti-concentration property of the supremum of the approximating Gaussian process, and we derive an inequality leading to such a property for separable Gaussian processes. We refer to the new condition as a generalized SBR condition. Our new result shows that the supremum does not concentrate too fast around any value. We then apply this result to derive a Gaussian multiplier bootstrap procedure for constructing honest confidence bands for nonparametric density estimators (this result can be applied in other nonparametric problems as well). An essential advantage of our approach is that it applies generically even in those cases where the limit distribution of the supremum of the studentized empirical process does not exist (or is unknown). This is of particular importance in problems where resolution levels or other tuning parameters have been chosen in a data-driven fashion, which is needed for adaptive constructions of the confidence bands. Finally, of independent interest is our introduction of a new, practical version of Lepski's method, which computes the optimal, nonconservative resolution levels via a Gaussian multiplier bootstrap method.

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