April 2021 Coverage of credible intervals in nonparametric monotone regression
Moumita Chakraborty, Subhashis Ghosal
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Ann. Statist. 49(2): 1011-1028 (April 2021). DOI: 10.1214/20-AOS1989


For nonparametric univariate regression under a monotonicity constraint on the regression function f, we study the coverage of a Bayesian credible interval for f(x0), where x0 is an interior point. Analysis of the posterior becomes a lot more tractable by considering a “projection-posterior” distribution based on a finite random series of step functions with normal basis coefficients as a prior for f. A sample f from the resulting conjugate posterior distribution is projected on the space of monotone increasing functions to obtain a monotone function f closest to f, inducing the “projection-posterior.” We use projection-posterior samples to obtain credible intervals for f(x0). We obtain the asymptotic coverage of the credible interval thus constructed and observe that it is free of nuisance parameters involving the true function. We observe a very interesting phenomenon that the coverage is typically higher than the nominal credibility level, the opposite of a phenomenon observed by Cox (Ann. Statist. 21 (1993) 903–923) in the Gaussian sequence model. We further show that a recalibration gives the right asymptotic coverage by starting from a lower credibility level that can be explicitly calculated.


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Moumita Chakraborty. Subhashis Ghosal. "Coverage of credible intervals in nonparametric monotone regression." Ann. Statist. 49 (2) 1011 - 1028, April 2021. https://doi.org/10.1214/20-AOS1989


Received: 1 March 2020; Revised: 1 June 2020; Published: April 2021
First available in Project Euclid: 2 April 2021

Digital Object Identifier: 10.1214/20-AOS1989

Primary: 62F15 , 62G05 , 62G08 , 62G10 , 62G15 , 62G20

Keywords: Chernoff’s distribution , coverage , Credible set , Monotonicity , Nonparametric regression , projection-posterior

Rights: Copyright © 2021 Institute of Mathematical Statistics


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Vol.49 • No. 2 • April 2021
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