ECON 221 Study Guide - Midterm Guide: Standard Deviation, Joint Probability Distribution
Document Summary
You can use the back pages for notes/scribble works: suppose x is the number of credit card purchases a person makes per week and y represents the number of credit card the person owns. The joint probability distribution of x and y is as follows: Find the probability of a person making 3 credit card purchases per week owns 2 cards. Find the probability of a randomly selected person owns 2 or fewer cards and also makes 2 or fewer purchases per week. F x,y (2,2) = (0. 08 +0. 10 +0. 10)+ (0. 08+ 0. 05+0. 22)=0. 28+ 0. 35=0. 63. Find the expected number of credit card purchases per week, e(x), and the expected number of cards a person owns, e(y). 2 (d) compute the covariance of x and y and show whether x and y are correlated or not. Note: the correlation coefficient, r = cov. (xy)/( x y) ; x = standard deviation of x; y = standard deviation of y.
