More precisely, suppose we have the following statements for a random variable X: (A) There is a > 0 such that E[ex] < +∞; Az (B) There is X>0 and m >0 such that P[|X| ≥ x] ≤ me¯ for all x ≥ 0. We show that (A) implies (B) (with m := E[eª|X] and À ≤ a in (B)) and that (B) implies (A) (with a in (A) being any number a € (0, A)), so that statement (A) and (B) are equivalent. (a) (A implies B) Suppose X is a random variable for which m := E[eª|X ] < +∞, where a > 0. Suppose ≥ 0 and define A(x) = {w: X(w) ≥ x} Show for any >> 0 that A(x) = {w: e^|x (w)| ≥ e^x}. (b) By considering the cases when w€ A(x) and w€ Ã(x), show that ex> e IA(z).

Calculus For The Life Sciences
2nd Edition
ISBN:9780321964038
Author:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Publisher:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Chapter12: Probability
Section12.CR: Chapter 12 Review
Problem 84CR
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More precisely, suppose we have the following statements for a random variable
X:
(A) There is a > 0 such that EleX]< +00;
(B) There is A> 0 and m > 0 such that P[|X| > x] < me™^* for all I > 0.
We show that (A) implies (B) (with m :=E[eX] and A < a in (B)) and that
(B) implies (A) (with a in (A) being any number a E (0, X)), so that statement
(A) and (B) are equivalent.
(a) (A implies B) Suppose X is a random variable for which m :=E[e* X ]<
+oo, where a > 0. Suppose x > 0 and define
A(x) = {w : |X(w)| > x}
Show for any > 0 that A(x) ={w:e\X(w)l > e}.
(b) By considering the cases when w E A(x) and w e A(x), show that e|X] >
(2)VI zx?
Transcribed Image Text:More precisely, suppose we have the following statements for a random variable X: (A) There is a > 0 such that EleX]< +00; (B) There is A> 0 and m > 0 such that P[|X| > x] < me™^* for all I > 0. We show that (A) implies (B) (with m :=E[eX] and A < a in (B)) and that (B) implies (A) (with a in (A) being any number a E (0, X)), so that statement (A) and (B) are equivalent. (a) (A implies B) Suppose X is a random variable for which m :=E[e* X ]< +oo, where a > 0. Suppose x > 0 and define A(x) = {w : |X(w)| > x} Show for any > 0 that A(x) ={w:e\X(w)l > e}. (b) By considering the cases when w E A(x) and w e A(x), show that e|X] > (2)VI zx?
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