We give a comparison inequality that allows one to estimate the tail probabilities of sums of independent Banach space valued random variables in terms of those of independent identically distributed random variables. More precisely, let X 1 X n be independent Banach-valued random variables. Let I
Comparison of Moments of Sums of Independent Random Variables and Differential Inequalities
✍ Scribed by S. Kwapień; R. Latała; K. Oleszkiewicz
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 463 KB
- Volume
- 136
- Category
- Article
- ISSN
- 0022-1236
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✦ Synopsis
For S= x i ! i , where (! i ) is a sequence of independent, symmetric random variables and (x i ) is a sequence of vectors in a normed space we give two methods of proving inequalities (E &S& p ) 1Âp C p, q (E &S& q ) 1Âq with the constants C p, q independent of the sequence (x i ). The methods depend on using differential inequalities of Poincare or logarithmic Sobolev type. The obtained constants are usually better than the ones obtained by other methods. 1996 Academic Press, Inc. I. Poincare Type Inequalities and Comparison of 2p, p Moments of S
Let I=(&a, a), 0<a and let M be a probability distribution on I with density function m which is continuous, positive, and symmetric on I. We will assume that M has the finite second moment, i.e., I s 2 M(ds)= I s 2 m(s) ds< . Let p, q, u: I [ R be defined by p(x)= a x sm(s) ds, q(x)=
x 0 (1Âp(s)) ds, u(x)=p(x)Âm(x). The functions p, u are positive, continuous, and symmetric on I. Let C 0 (I) denote the class of smooth functions on I with compact supports contained in I. For f # C 0 (I) we define Lf (x)=xf $(x)&u(x) f "(x)= &(1Âm(x))( pf $)$ (x). The operator L is formally symmetric in L 2 (I, M) and we have
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In this paper, it is shown that a convolution of uniform distributions (a) is more dispersed and (b) has a smaller hazard rate when the scale parameters of the uniform distributions are more dispersed in the sense of majorization. It is also shown that a convolution of gamma distributions with a com
## I. fntFoduction Let {X,,, n 2 1) be a sequence of independent random variables, P, and f, the distribution function and the characteristic fundion of the X,, respectively. Let us put SN = 2 X,, where N is a pasitive integer-valued random variable independent of X,, ?t 2 1. Furthermore, let { P,