title: ASYMPTOTICS FOR CHANGE-POINT MODELS UNDER VARYING DEGREES OF MIS-SPECIFICATION.
abstract: Change-point models are widely used by statisticians to model drastic changes in the pattern of observed data. Least squares/maximum likelihood based estimation of change-points leads to curious asymptotic phenomena. When the change-point model is correctly specified, such estimates generally converge at a fast rate (n) and are asymptotically described by minimizers of a jump process. Under complete mis-specification by a smooth curve, i.e. when a change-point model is fitted to data described by a smooth curve, the rate of convergence slows down ton1/3and the limit distribution changes to that of the minimizer of a continuous Gaussian process. In this paper we provide a bridge between these two extreme scenarios by studying the limit behavior of change-point estimates under varying degrees of model mis-specification by smooth curves, which can be viewed as local alternatives. We find that the limiting regime depends on how quickly the alternatives approach a change-point model. We unravel a family of 'intermediate' limits that can transition, at least qualitatively, to the limits in the two extreme scenarios. The theoretical results are illustrated via a set of carefully designed simulations. We also demonstrate how inference for the change-point parameter can be performed in absence of knowledge of the underlying scenario by resorting to subsampling techniques that involve estimation of the convergence rate.
authors.affiliation: North Carolina State University, University of Michigan and University of North Carolina.
authors.forename: Rui
authors.initials: R
authors.lastname: Song
authors.affiliation: North Carolina State University, University of Michigan and University of North Carolina.
authors.forename: Moulinath
authors.initials: M
authors.lastname: Banerjee
authors.affiliation: North Carolina State University, University of Michigan and University of North Carolina.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kosorok
keywords: Change-point; Model mis-specification