Chapter 1: Problem 3
For each of the following distributions, compute \(P(\mu-2 \sigma
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Chapter 1: Problem 3
For each of the following distributions, compute \(P(\mu-2 \sigma
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Let \(X\) denote a random variable such that \(K(t)=E\left(t^{X}\right)\) exists for all real values of \(t\) in a certain open interval that includes the point \(t=1 .\) Show that \(K^{(m)}(1)\) is equal to the \(m\) th factorial moment \(E[X(X-1) \cdots(X-m+1)]\).
Suppose \(C_{1}, C_{2}, C_{3}, \ldots\) is a nondecreasing sequence of sets, i.e., \(C_{k} \subset C_{k+1}\), for \(k=1,2,3, \ldots\) Then \(\lim _{k \rightarrow \infty} C_{k}\) is defined as the union \(C_{1} \cup C_{2} \cup C_{3} \cup \cdots\). Find \(\lim _{k \rightarrow \infty} C_{k}\) if (a) \(C_{k}=\\{x: 1 / k \leq x \leq 3-1 / k\\}, k=1,2,3, \ldots\). (b) \(C_{k}=\left\\{(x, y): 1 / k \leq x^{2}+y^{2} \leq 4-1 / k\right\\}, k=1,2,3, \ldots\)
Find the mean and variance, if they exist, of each of the following
distributions.
(a) \(p(x)=\frac{3 !}{x !(3-x) !}\left(\frac{1}{2}\right)^{3}, x=0,1,2,3\), zero
elsewhere.
(b) \(f(x)=6 x(1-x), 0
If the pdf of \(X\) is \(f(x)=2 x e^{-x^{2}}, 0
Let a random variable \(X\) of the continuous type have a pdf \(f(x)\) whose graph is symmetric with respect to \(x=c .\) If the mean value of \(X\) exists, show that \(E(X)=c\) Hint: Show that \(E(X-c)\) equals zero by writing \(E(X-c)\) as the sum of two integrals: one from \(-\infty\) to \(c\) and the other from \(c\) to \(\infty\). In the first, let \(y=c-x\); and, in the second, \(z=x-c\). Finally, use the symmetry condition \(f(c-y)=f(c+y)\) in the first.
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