Solution :
Var(Y) = 1/9 V(X) + V(X)
= 1/9 * 3 + 3
= 1/3 + 3
= 10 / 3
Variance of Y = 10/3 = 3.333
If E(X) = 5, V(X) = 3, and Y = 5 - - X, what is the mean of Y?
E = "Expected Value"
V = "Variance"
0 < x < 00, x < y < oo IS joint probability density function a) Compute the probability that X < 1 and Y < 2. b) Find E(X) c) Find E(Y d) Find V(X) e) Find V(Y)
Suppose X and Y V(X) = 3 and V(Y ) = 5. Find: (a) V(X + Y ) given that X, Y are independent (b) V(3X + 4) given that X, Y are independent (c) V(X + X) given that E(X · Y ) = −1 (d) V(X + 3Y ) given that E(X · Y ) = 0
1. Suppose X has mean 3 and variance 4, Y has mean 5 and variance 9, and Coy(X, Y) =-2. (a) What is the mean of 6X 7Y? (b) What is the variance of 6X TY? (c) What is the variance of 6X - TY? (d) What is the squared coefficient of variation of X? (e) What is the covariance of X and X +Y?
Let the variance of random variable X be 3, the variance of Y be 12, and the variance of Z be 9, and let X, Y , and Z be uncorrelated. Find V ar(4 − 2X + 3Y − 10Z).
Two random variables X and Y have means E[X] = 1 and E[Y] = 0, variances 0x2 = 9 and Oy2 = 4, and a correlation coefficient xx =0.6. New random variables are defined by V = -2X + Y W = 2X + 2Y Find the means of V and W Find the variances of V and W defined in question 3 Find Rww for the variables V and W defined in question 3
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,...
given that e(x)=55, e(y)=24, variance (x)=380, variance(y)=1200, standard deviation (x,y)=500 calculate the correlation coefficient
1. Suppose that E(X) E(Y) E(Z) 2 Y and Z are independent, Cov(X, Y) V(X) V(Z) 4, V(Y) = 3 Let U X 3Y +Z and W = 2X + Y + Z 1, and Cov(X, Z) = -1 Compute E(U) and V (U) b. Compute Cov(U, W). а.
3. (30pt) Suppose that E(Y) = 1, E(Y2) = 2, E(Y3) = 3, V(Y1) = 6, V(Y2) = 7,V (Y3) = 8, Cov(Yı, Y2) = 0, Cov(Yı, Y3) = -4 and 10 1 2 3 Cov(Y2, Y3) = 5. Also define a = 20 and A = 4 5 6 30/ ( 7 8 9 (a) (10pt) Find the expected value and variance covariance matrix of Y, where Y = Y2 (b) (10pt) Compute Eſa'Y) and E(AY). (c) (10pt) Compute...