(3) Let X = (X1, X2) be a two-dimensional random vector with variance Var[X= 121 12]...
12. Let X1,... , X5 be random variables with variance 4, and let Find Var(X1 X2+X3 + X4 +X5);
kercise 6. (Rossi 2.6.4, 2.6.29) (a) Let X - (X1, X2) be a random vector with probability density function given by f(x1,x2) = 24x1x2 with support determined by 0 < xit x2 < 1,띠 > 0,x2 > 0 Determine each of the following. (v) Var(Xi/X2) (vi) ElVar(X1|X2)]
3. You may use this fact throughout: For any scalars a, a2,a3 and random variables .X2, X3: (a) If Cov (Xi, X2) Cov (X2, X3)-p, Cov (Xi, X3)-p and Var(X1,2,3, then write the 3 x 3 covariance matrix of the random vector X = (X1,X2,X3). (b) Compute Var(Xi X2+X3) when p 0.6. (e) Mark is interested in forecasting X using the linear predictor &bbX He realizes the forecast error is X - X X bX2 -bX and a great way...
2. Let X1, X2,. . , Xn denote independent and identically distributed random variables with variance σ2, which of the following is sufficient to conclude that the estimator T f(Xi, , Xn) of a parameter 6 is consistent (fully justify your answer): (a) Var(T) (b) E(T) (n-1) and Var(T) (c) E(T) 6. (d) E(T) θ and Var(T)-g2. 72 121
how to calculate cov(x1,x2), cov(x2,x3),cov(x3,x1)? and how to calculate var(x1),var(x2),var(x3)? Given three random variables Xi, X2, and X such that X[Xi X2 X 20 -1 E [X] ,1-10 | and var(X)=Σ-| 0 3 0. 1 0.5 1 compuite: 2
O. Let X1 and X2 be two random variables, and let Y = (X1 + X2)2. Suppose that E[Y ] = 25 and that the variance of X1 and X2 are 9 and 16, respectively. O. Let Xi and X2 be two random variables, and let Y = (X1 X2)2. Suppose that and that the variance of X1 and X2 are 9 and 16, respectively E[Y] = 25 (63) Suppose that both X\ and X2 have mean zero. Then the...
5. Let X1,X2, . , Xn be a random sample from a distribution with finite variance. Show that (i) COV(Xi-X, X )-0 f ) ρ (Xi-XX,-X)--n-1, 1 # J, 1,,-1, , n. OV&.for any two random variables X and Y) or each 1, and (11 CoV(X,Y) var(x)var(y) (Recall that p vararo 5. Let X1,X2, . , Xn be a random sample from a distribution with finite variance. Show that (i) COV(Xi-X, X )-0 f ) ρ (Xi-XX,-X)--n-1, 1 # J,...
Let X be a 4-dimensional random vector defined as X = [X1 correlation matrix X4' with expected value vector and X2 X3 E[X] =| | , 1 1 -1 0 Rx-10-11-1 0 0 0-1 1 Let Y be a 3-dimensional random vector with (a) Find a matrix A such that Y -AX. (b) Find the correlation matrix of Y, that is Ry (c) Find the correlation matrix between X1 and Y, that is Rx,Y
= e B and cumu- Let X1, X2, ..., Xn be a random sample where X; has a probability density function f(x) lative density function F(x) = 1 - e B. Consider the following two estimators of B: х Bi = X1 B2 = (a) [2 points] Compute the relative efficiency of @1 to ộ2. (b) [1 point] Interpret the relative efficiency of ß1 to ß2 for a sample of size n = - 30.
Let X1, X2, , xn are independent random variables where E(X)-? and Var(X) ?2 for all i = 1, 2, , n. Let X-24-xitx2+--+Xy variables. is the average of those random Find E(X) and Var(X).