Question

In: Statistics and Probability

Let X1,...,Xn be independent random variables,and let X=X1+...+Xn be their sum. 1. Suppose that each Xi...

Let X1,...,Xn be independent random variables,and let X=X1+...+Xn be their sum.

1. Suppose that each Xi is geometric with respective parameter pi. It is known that the mean of X is equal to μ, where μ > 0. Show that the variance of X is minimized if the pi's are all equal to n/μ.

2. Suppose that each Xi is Bernoulli with respective parameter pi. It is known that the mean of X is equal to μ, where μ > 0. Show that the variance of X is maximized if the pi's are all equal to μ/n.

Solutions

Expert Solution


Related Solutions

Problem 1 Let X1, X2, . . . , Xn be independent Uniform(0,1) random variables. (...
Problem 1 Let X1, X2, . . . , Xn be independent Uniform(0,1) random variables. ( a) Compute the cdf of Y := min(X1, . . . , Xn). (b) Use (a) to compute the pdf of Y . (c) Find E(Y ).
2. Let X1, X2, . . . , Xn be independent, uniformly distributed random variables on...
2. Let X1, X2, . . . , Xn be independent, uniformly distributed random variables on the interval [0, θ]. (a) Find the pdf of X(j) , the j th order statistic. (b) Use the result from (a) to find E(X(j)). (c) Use the result from (b) to find E(X(j)−X(j−1)), the mean difference between two successive order statistics. (d) Suppose that n = 10, and X1, . . . , X10 represents the waiting times that the n = 10...
Let X1,…, Xn be a sample of iid random variables with pdf f (x; ?1, ?2)...
Let X1,…, Xn be a sample of iid random variables with pdf f (x; ?1, ?2) = ?1 e^(−?1(x−?2)) with S = [?2, ∞) and Θ = ℝ+ × ℝ. Determine a) L(?1, ?2). b) the MLE of ?⃗ = (?1, ?2). c) E(? ̂ 2).
Let X1,...,Xn be exponentially distributed independent random variables with parameter λ. (a) Find the pdf of...
Let X1,...,Xn be exponentially distributed independent random variables with parameter λ. (a) Find the pdf of Yn= max{X1,...,Xn}. (b) Find E[Yn]. (c) Find the median of Yn. (d) What is the mean for n= 1, n= 2, n= 3? What happens as n→∞? Explain why.
Let X1, … , Xn be independent where Xi is normally distributed with unknown mean µ...
Let X1, … , Xn be independent where Xi is normally distributed with unknown mean µ and unknown variance o2 > 0. Find the likelihood ratio test for testing that µ = 0 against −∞ < µ < ∞.
Let X1, … , Xn be independent where Xi is normally distributed with unknown mean µ...
Let X1, … , Xn be independent where Xi is normally distributed with unknown mean µ and unknown variance o2 > 0. Find the likelihood ratio test for testing that µ = 0 against −∞ < µ < ∞.
Let X1, ..., Xn be i.i.d random variables with the density function f(x|θ) = e^(θ−x) ,...
Let X1, ..., Xn be i.i.d random variables with the density function f(x|θ) = e^(θ−x) , θ ≤ x. a. Find the Method of Moment estimate of θ b. The MLE of θ (Hint: Think carefully before taking derivative, do we have to take derivative?)
Let X1, X2, . . . , Xn be iid Poisson random variables with unknown mean...
Let X1, X2, . . . , Xn be iid Poisson random variables with unknown mean µ 1. Find the maximum likelihood estimator of µ 2.Determine whether the maximum likelihood estimator is unbiased for µ
Let X1, X2, X3, . . . be independently random variables such that Xn ∼ Bin(n,...
Let X1, X2, X3, . . . be independently random variables such that Xn ∼ Bin(n, 0.5) for n ≥ 1. Let N ∼ Geo(0.5) and assume it is independent of X1, X2, . . .. Further define T = XN . (a) Find E(T) and argue that T is short proper. (b) Find the pgf of T. (c) Use the pgf of T in (b) to find P(T = n) for n ≥ 0. (d) Use the pgf of...
R simulation: Let X1, . . . , Xn be i.i.d. random variables from a uniform...
R simulation: Let X1, . . . , Xn be i.i.d. random variables from a uniform distribution on [0, 2]. Generate and plot 10 paths of sample means from n = 1 to n = 40 in one figure for each case. Give some comments to empirically check the Law of Large Numbers. (a) When n is large, X1 + · · · + Xn/n  converges to E[Xi]. (b) When n is large, X1^2+ · · · + Xn^2/n converges to...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT