Introduction to Econometrics 3rd Edition by James Stock, Mark Watson

تمرين 9

In a given population of two-earner male/female couples, male earnings have a mean of $40,000 per year and a standard deviation of $12,000. Female earnings have a mean of $45,000 per year and a standard deviation of $18,000. The correlation between male and female earnings for a couple is 0.80. Let C denote the combined earnings for a randomly selected couple.
a. What is the mean of C
b. What is the covariance between male and female earnings
c. What is the standard deviation of C
d. Convert the answers to (a) through (c) from U.S. dollars ($) to euros (€).