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Suppose that the random variable Xis equal to the number of hits obtained by a certain baseball player in his next 3at-bats. If P{X=1}=3,P{X=2}=2andP{X=0}=3P{X=3}, find E[X].

Short Answer

Expert verified

The value ofE[X]is=1.075.

Step by step solution

01

Given Information

Given in the question that,

P(X=1)=0.3

P(X=2)=0.2

P(X=0)=3P(X=3)

02

Solution of the Problem

We know that

P(X=0)+P(X=1)+P(X=2)+P(X=3)=1

0.5+4P(X=3)=1

Find the value,

P(X=3)=0.125

P(X=0)=30.125=0.375

03

Computation of the Value

Find the value

XiPi00.37510.320.230.125

E(X)=xipi

=00.375+10.3+20.2+30.125

=1.075.

04

Final Answer

The value ofE(X)is1.075.1.075.

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Most popular questions from this chapter

Let Xbe a Poisson random variable with parameter . Show that PX=iincreases monotonically and then decreases monotonically asiincreases, reaching its maximum when iis the largest integer not exceeding .

Hint: Consider PX=i/PX=i1.

An urn initially contains one red and one blue ball. At each stage, a ball is randomly chosen and then replaced along with another of the same color. Let X denote the selection number of the 铿乺st chosen ball that is blue. For instance, if the 铿乺st selection is red and the second blue, then X is equal to 2.

  • (a) Find P{X>i},i1
  • (b) Show that with probabilityrole="math" 1, a blue ball is eventually chosen. (That is, show thatP{X<}=1.)
  • (c) FindE[X].

In the game of Two-Finger Morra, 2players show 1or 2fingers and simultaneously guess the number of fingers their opponent will show. If only one of the players guesses correctly, he wins an amount (in dollars) equal to the sum of the fingers shown by him and his opponent. If both players guess correctly or if neither guesses correctly, then no money is exchanged. Consider a specified player, and denote by X the amount of money he wins in a single game of Two-Finger Morra.

(a) If each player acts independently of the other, and if each player makes his choice of the number of fingers he will hold up and the number he will guess that his opponent will hold up in such a way that each of the 4possibilities is equally likely, what are the possible values of Xand what are their associated probabilities?

(b) Suppose that each player acts independently of the other. If each player decides to hold up the same number of fingers that he guesses his opponent will hold up, and if each player is equally likely to hold up 1or 2 fingers, what are the possible values ofX and their associated probabilities?

Suppose that the distribution function of X given by

F(b)=0鈥呪赌呪赌呪赌b<0b4鈥呪赌呪赌呪赌0b<112+b14鈥呪赌呪赌呪赌1b<21112鈥呪赌呪赌呪赌2b<31鈥呪赌呪赌呪赌3b

(a) Find P{X=i},i=1,2,3.

(b) Find P12<X<32.

Consider ncoins, each of which independently comes up heads with probability p. Suppose that nis large and pis small, and let =np. Suppose that all ncoins are tossed; if at least one comes up heads, the experiment ends; if not, we again toss all coins, and so on. That is, we stop the first time that at least one of the ncoins come up heads. Let Xdenote the total number of heads that appear. Which of the following reasonings concerned with approximating P{X=1}is correct (in all cases, Yis a Poisson random variable with parameter )?

(a) Because the total number of heads that occur when all ncoins are rolled is approximately a Poisson random variable with parameter ,

P{X=1}P{Y=1}=e-

(b) Because the total number of heads that occur when all ncoins are rolled is approximately a Poisson random variable with parameter , and because we stop only when this number is positive,

P{X=1}P{Y=1Y>0}=e-1-e-

(c) Because at least one coin comes up heads, Xwill equal 1 if none of the other n-1coins come up heads. Because the number of heads resulting from these n-1coins is approximately Poisson with mean (n-1)p,

P{X=1}P{Y=0}=e-

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