Asymptotic independence of three statistics of maximal segmental scores
File(s)1402.5858v1.pdf (185.18 KB)
Accepted version
Author(s)
Mijatović, A
Pistorius, M
Type
Journal Article
Abstract
Let $\xi_1,\xi_2,\ldots$ be an iid sequence with negative mean. The
$(m,n)$-segment is the subsequence $\xi_{m+1},\ldots,\xi_n$ and its
\textit{score} is given by $\max\{\sum_{m+1}^n\xi_i,0\}$. Let $R_n$ be the
largest score of any segment ending at time $n$, $R^*_n$ the largest score of
any segment in the sequence $\xi_{1},\ldots,\xi_n$, and $O_x$ the overshoot of
the score over a level $x$ at the first epoch the score of such a size arises.
We show that, under the Cram\'er assumption on $\xi_1$, asymptotic independence
of the statistics $R_n$, $R_n^* -y$ and $O_{x+y}$ holds as
$\min\{n,y,x\}\to\infty$. Furthermore, we establish a novel Spitzer-type
identity characterising the limit law $O_\infty$ in terms of the laws of
$(1,n)$-scores. As corollary we obtain: (1) a novel factorization of the
exponential distribution as a convolution of $O_\infty$ and the stationary
distribution of $R$; (2) if $y=\gamma^{-1}\log n$ (where $\gamma$ is the
Cram\'er coefficient), our results, together with the classical theorem of
Iglehart \cite{Iglehart}, yield the existence and explicit form of the joint
weak limit of $(R_n, R_n^* -y,O_{x+y})$.
$(m,n)$-segment is the subsequence $\xi_{m+1},\ldots,\xi_n$ and its
\textit{score} is given by $\max\{\sum_{m+1}^n\xi_i,0\}$. Let $R_n$ be the
largest score of any segment ending at time $n$, $R^*_n$ the largest score of
any segment in the sequence $\xi_{1},\ldots,\xi_n$, and $O_x$ the overshoot of
the score over a level $x$ at the first epoch the score of such a size arises.
We show that, under the Cram\'er assumption on $\xi_1$, asymptotic independence
of the statistics $R_n$, $R_n^* -y$ and $O_{x+y}$ holds as
$\min\{n,y,x\}\to\infty$. Furthermore, we establish a novel Spitzer-type
identity characterising the limit law $O_\infty$ in terms of the laws of
$(1,n)$-scores. As corollary we obtain: (1) a novel factorization of the
exponential distribution as a convolution of $O_\infty$ and the stationary
distribution of $R$; (2) if $y=\gamma^{-1}\log n$ (where $\gamma$ is the
Cram\'er coefficient), our results, together with the classical theorem of
Iglehart \cite{Iglehart}, yield the existence and explicit form of the joint
weak limit of $(R_n, R_n^* -y,O_{x+y})$.
Date Issued
2015-01-15
Citation
Statistics & Probability Letters, 2015
ISSN
0167-7152
Publisher
Elsevier
Start Page
185
End Page
191
Journal / Book Title
Statistics & Probability Letters
Volume
99
Copyright Statement
© 2015 Elsevier B.V. All rights reserved. NOTICE: this is the author’s version of a work that was accepted for publication in Statistics & Probability Letters. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in STATISTICS & PROBABILITY LETTERS, Vol.: 99 (2015) DOI: 10.1016/j.jeurceramsoc.2014.02.008
Description
25.03.15 KB. OK to add accepted version to spiral, subject to 12 months embargo
Identifier
http://arxiv.org/abs/1402.5858v1
Subjects
math.PR
math.PR
60G51
Notes
13 pages, no figures
Publication Status
Accepted