Diffusions with measurement errors. I. Local Asymptotic Normality

Author: Gloter Arnaud   Jacod Jean  

Publisher: Edp Sciences

E-ISSN: 1262-3318|5|issue|225-242

ISSN: 1292-8100

Source: ESAIM: Probability and Statistics, Vol.5, Iss.issue, 2010-03, pp. : 225-242

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Abstract

We consider a diffusion process X which is observed at times i/nfor i = 0,1,...,n, each observation being subject to a measurementerror. All errors are independent and centered Gaussian with knownvariance pn. There is an unknown parameter within the diffusioncoefficient, to be estimated. In this first paper thecase when X is indeed a Gaussian martingale is examined: we can provethat the LAN property holds under quite weak smoothness assumptions,with an explicit limiting Fisher information. What is perhaps the mostinteresting is the rate at which this convergence takes place:it is $1/\sqrt{n}$ (as when there is no measurement error) when pn goes fastenough to 0, namely npn is bounded. Otherwise, and provided thesequence pn itself is bounded, the rate is (pn / n)1/4. Inparticular if pn = p does not depend on n, we get a rate n-1/4.