CHAPTER 9
Probability and Random Variables
Organizers of a high school class reunion conducted a survey of the 385 graduates. Among the
questions asked were “How many children do you have?” and “Do you have any pets?” The data are
summarized in the table.
What is the probability that a randomly selected graduate owns a pet, given that the person has 3 or 4
children?
(A) 0.070
(B) 0.175
(C) 0.216
(D) 0.424
(E) 0.784
A particular game awards points with the following probabilities:
E (x ) = 10 and s (x ) = 5. What is the standard deviation of the total number of points after 3
independent turns at this game?