Chapter 11: Problem 2
Give a method for simulating a negative binomial random variable.
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Chapter 11: Problem 2
Give a method for simulating a negative binomial random variable.
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If \(f\) is the density function of a normal random variable with mean \(\mu\) and variance \(\sigma^{2}\), show that the tilted density \(f_{t}\) is the density of a normal random variable with mean \(\mu+\sigma^{2} t\) and variance \(\sigma^{2}\).
Suppose it is relatively easy to simulate from \(F_{i}\) for each \(i=1, \ldots,
n\). How can we simulate from
(a) \(F(x)=\Pi_{i=1}^{n} F_{i}(x) ?\)
(b) \(F(x)=1-\Pi_{i=1}^{n}\left(1-F_{i}(x)\right)\) ?
(c) Give two methods for simulating from the distribution \(F(x)=x^{n}\),
\(0
Verify that if we use the hazard rate approach to simulate the event times of a nonhomogeneous Poisson process whose intensity function \(\lambda(t)\) is such that \(\lambda(t) \leq \lambda\), then we end up with the approach given in method 1 of Section \(11.5 .\)
Let \(X_{1,+\cdots}, X_{n}\) be independent random variables with \(E\left[X_{i}\right]=\theta\), \(\operatorname{Var}\left(X_{i}\right)=\sigma_{i}^{2}, i=1, \ldots, n\), and consider estimates of \(\theta\) of the form \(\sum_{i=1}^{n} \lambda_{i} X_{i}\) where \(\sum_{i=1}^{n} \lambda_{i}=1 .\) Show that \(\operatorname{Var}\left(\sum_{i=1}^{n} \lambda_{i} X_{i}\right)\) is minimized when \(\lambda_{i}=\left(1 / \sigma_{i}^{2}\right) /\left(\sum_{j=1}^{n} 1 / \sigma_{j}^{2}\right), i=1, \ldots, n\) Possible Hint: If you cannot ?o this for general \(n\), try it first when \(n=2\) The following two problems are concerned with the estimation of \(\int_{0}^{1} g(x) d x=E[g(U)]\) where \(U\) is uniform \((0,1) .\)
For a nonhomogeneous Poisson process with intensity function \(\lambda(t)\), \(t \geq 0\), where \(\int_{0}^{\infty} \lambda(t) d t=\infty\), let \(X_{1}, X_{2}, \ldots\) denote the sequence of times at which events occur. (a) Show that \(\int_{0}^{x_{1}} \lambda(t) d t\) is exponential with rate 1 . (b) Show that \(\int_{X_{i}-1}^{X_{j}} \lambda(t) d t, i \geq 1\), are independent exponentials with rate 1, where \(X_{0}=0\). In words, independent of the past, the additional amount of hazard that must be experienced until an event occurs is exponential with rate \(1 .\)
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