Let X and Y be the daily sales of Super-Laser printers at the
Burtonville and the Arbortown outlets of a
consumer electronics department store chain. Suppose that
E(X) = 25.0 and E(Y) = 33.1,
SD(X) = 7.0 and SD(Y) = 6.2,
and COV(X, Y) = 17.7.
What is CORR(X, Y)?
Let X and Y be the daily sales of Super-Laser printers at the Burtonville and the...
20. For X let E(X)-0 and sd(x)-2, and for Y let E(Y)--1 and sd(Y)-4. Find: (a) E(X-Y) and E (X Y). (b) Var(X- Y) and Var(X+ Y) if X and Y are independent. (c) EGX+ 흘 Y) and Var(1X+] Y) İf X and Y are independent. (d) Repeat (b) if, instead of independence, Cov(X, Y)- 1. soY is VarY larger
= Var(X) and σ, 1. Let X and Y be random variables, with μx = E(X), μY = E(Y), Var(Y). (1) If a, b, c and d are fixed real numbers, (a) show Cov (aX + b, cY + d) = ac Cov(X, Y). (b) show Corr(aX + b, cY +d) pxy for a > 0 and c> O
Let X and Y b Var(Y) (1) If a, b,c and d are fixed real numbers, = E(X), μγ E (Y),咳= Var(X) and e ranclom variables. with y a) show Cov(aX +b, cY +d)- ac Cov(X,Y) (b) show Corr(aX + b, cY + d)-PXY for a > 0 and c > 0.
Exercise 2 (2). Let X and ε be independent normally distributed random variables such that X∼N(5,4)andε∼N(0,9).LetY bearandomvariablegivenbyY =1+2X+ε.Compute: (a) E(Y ) (b) Var(Y ) (c) Cov(X, Y ) (d) Corr(X, Y ) (e) What is the value of the ratio Cov(X, Y )/Var(X) ? (f) If Y = 1 + 3X + ε instead, what would be the value of Cov(X, Y )/Var(X) ? (g) If Y = 1 + 7X + ε instead, what would be the value of...
Let the frequency function of the joint distribution of the random variables X and Y P(X = 2, Y = 3) = P(X = 1, Y = 2) = P(X = -1, Y = 1) = P(X = 0, Y = -1) = P(X = -1, Y = -2) = 3 a) Determine the marginal distributions of the random variables X and Y. b) Determine Cov(X,Y) and Corr(X,Y). c) Determine the conditional distributions of the random variable Y as a...
1. Let the joint probability (mass) function of X and Y be given by the following: Value of X -1 -1 3/8 1/8 Value of Y1 1/8 3/8 (a) Determine the marginal (b) Determine the conditional distribution of X given Y (c) Are they independent? d) Compute E(X), Var(X), E(Y) and Var(Y). (e) Compute PXY <0) and Ptmax(X,Y) > 0 (f) Compute Elmax(X, Y)] and E(XY) (g) Compute Cov(X,Y) and Corr(X, Y) 1
Consider n = 5 pairs (x! ,y, , . . . , (xt, y,'). Let x = n-ı Σ i , and y = n-ı Σ -1 y be the sample means of the x and y variables. Let & and Sy be the corresponding standard deviations. Let sry and rry be the sample covariance and sample correlation respective . Suppose x = 6.2,J = 8 8 2.95, sy4.494, sy 13.05. Part a) What is the sample correlation of the...
Management proposed the following regression model to predict sales at a fast-food outlet. y Po+ BBx, +B,x, +e where number of competitors within one mile x, x2 population within one mile (1000s) drive-up window present l0 otherwise y sales ($1000s) The following estimated regression equation was developed after 20 outlets were surveyed. i-10.5-4.3 +6.2 +15.5z3 a. What is the expected amount of sales attributable to the drive-up window? b. Predict sales for a store with two competitors, a population of...
2. The joint density of X and Y is given by Say 0SX S1,0 Sy sa fxy(x,y) = {o otherwise. (a) Find fxiy (ay). (b) Set up the integrals (do not evaluate) for evaluating Cov(X,Y). 3. In this question, you will identify the distribution of the sum of independent random variables. I expect you will find that the mgf approach is your friend. (a) Let X and Y be independent Poisson random variables with means X, and A2, respectively, and...
Let X and Y have the following joint distribution X/Y 0 1 0 0.4 0.1 1 0.1 0.1 2 0.1 0.2 a) Find Cov(4+2X, 3-2Y) b) Let Z = 3X-2Y+2 Find E[Z] and σ 2Z c) Calculate the correlation coefficient between X and Y. What does this suggest about the relationship between X and Y? d) Show that for two nonzero constants a and b Cov(X+a, Y+b) = Cov(X,Y)