Exponential inequalities for self-normalized processes with applications
Victor H de la Peña, Columbia University
Guodong Pang, Columbia University
Abstract
We prove the following exponential inequality for a pair of random variables $(A,B)$ with $B >0$ satisfying the textit{canonical assumption}, $E[exp(lambda A - frac{lambda^2}{2} B^2)] leq 1$ for $lambda in RR$,
begin{equation*}
Pleft( frac{|A|}{sqrt{ frac{2q-1}{q} left(B^2+ (E[|A|^p])^{2/p} right) }} geq x right) leq left(frac{q}{2q-1} right)^{frac{q}{2q-1}} x^{-frac{q}{2q-1}} e^{-x^2/2}
end{equation*}
for $x>0$,
where $1/p+ 1/q =1$ and $pgeq1$. Applying this inequality, we obtain exponential bounds for the tail probabilities for self-normalized martingale difference sequences. We propose a method of hypothesis testing for the $L^p$-norm $(p geq 1)$ of $A$ (in particular, martingales) and some stopping times. We apply this inequality to the stochastic TSP in $[0,1]^d$ ($dgeq 2$), connected to the CLT.
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