STATISTICS & PROBABILITY LETTERS, cilt.78, sa.18, ss.3152-3158, 2008 (SCI-Expanded)
Let X and Y be two random variables which are independently and identically distributed (i.i.d.) as exponential. Given two nonnegative numbers a and b, it is of interest to establish bounds on the tail probability of aX + bY, i.e. P (aX + bY > t). The present work attempts to provide first some basic inequalities for P (aX + bY > t) and then shows that this probability increases in (a. b) defined on the set D = {(a, b) : a(2) + b(2) = 1, a > b} for some t. This result is further supported and enhanced by numerical computation. (C) 2008 Elsevier B.V. All rights reserved.