4.10 Do people of different age groups differ in their response to email messages? A survey by the Center for the Digital Future of the University of Southern California (data extracted from A. Mindlin, "Older E-mail Users Favor Fast Replies," The New York Times, July 14, 2008, p. B3) reported that 70.4% of users over 70 years of age believe that email messages should be answered quickly, as compared to 154 CHAPTER 4 Basic Probability 54.8% of users 13 to 50 years old. Suppose that the survey was based on 1,000 users over 70 years of age and 1,000 users 13 to 50 years old. The following table summarizes the results: COUNTRY ENGAGEMENT United States Germany Total Engaged 550 246 796 Not engaged 1,345 1,649 2,994 Total 1,895 1,895 3,790 Source: Data extracted from M. Nink, "Employee Disengagement Plagues Germany," Gallup Management Journal, gmj.gallup.com, April 9, 2009. AGE OF RESPONDENTS ANSWERS QUICKLY 12-50 Over 70 Total Yes 536 707 1,243 No 464 293 757 Total 1,000 1,000 2,000
a. Give an example of a simple event.
b. Give an example of a joint event.
c. What is the complement of a respondent who answers quickly?
d. Why is a respondent who answers quickly and is over 70 years old a joint event?