Section 2.1 Graphical Summaries for Qualitative Data 47 27. Music sales: The following frequency distribution presents the number of units sold for categories of physical and digital music in the years 2007 and 2008. The Mobile category refers to ringtones and other music downloaded to a mobile device. The category “Other” includes CD singles, cassettes, DVDs, and download albums. Sales (in millions) Type of Music 2007 2008 CDs 511 385 Download single 810 1033 Mobile 362 338 Other 117 50 Source: Recording Industry Association of America a. Construct a relative frequency distribution for the 2007 sales. b. Construct a relative frequency distribution for the 2008 sales. c. Construct a side-by-side relative frequency bar graph to compare the sales in 2007 and 2008. d. True or false: More than half of all sales in 2008 were download singles. 28. Bought a new car lately? The following table presents the number of vehicles sold in the United States by several manufacturers in March 2009 and March 2010. Manufacturer 2009 2010 General Motors 154,069 188,011 Ford 124,744 178,188 Chrysler LLC 101,001 92,623 Toyota 132,802 186,863 Honda 88,379 108,262 Nissan 66,634 95,468 Source: The Wall Street Journal a. Construct a relative frequency distribution for the 2009 sales. b. Construct a relative frequency distribution for the 2010 sales. c. Construct a side-by-side relative frequency bar graph to compare the sales in 2009 and 2010. d. True or false: For every manufacturer, sales were higher in 2010 than in 2009. 29. What are you reading? The following frequency distribution presents the number of subscriptions to four popular travel magazines in the spring of 2008. Magazine Subscribers (in thousands) A.F.’s Budget Travel 620 Cond´e Nast Traveler 796 National Geographic Traveler 670 Travel & Leisure 956 Source: Mediaweek a. Construct a frequency bar graph. b. Construct a relative frequency distribution. c. Construct a relative frequency bar graph. d. Construct a pie chart. e. What proportion of subscriptions are to Travel & Leisure? 30. The latest news: According to the Pew Research Center, there were 199 online news sites with more than 500,000 monthly unique visitors in 2009. The following table presents the number of sites in each of several categories. Type of Site Frequency Newspaper 95 Online only 66 Magazine 11 Local TV 10 Other 17 Source: The Pew Research Center a. Construct a frequency bar graph for these data. b. Construct a relative frequency distribution. c. Construct a relative frequency bar graph. d. Construct a pie chart. e. What proportion of online sites are associated with newspapers? Extending the Concepts 31. Native languages: The following frequency distribution presents the number of households (in thousands) categorized by the language spoken at home, for the cities of New York and Los Angeles in the year 2006. The Total column presents the numbers of households in both cities combined. Language New York Los Angeles Total English 3982 1384 5366 Spanish 1884 1539 3423 Other Indo-European 998 244 1242 Asian and Pacific Island 546 277 823 Source: U.S. Census Bureau a. Construct a frequency bar graph for each city. b. Construct a frequency bar graph for the total. c. Construct a relative frequency bar graph for each city. d. Construct a relative frequency bar graph for the total. e. Explain why the heights of the bars for the frequency bar graph for the total are equal to the sums of the heights for the individual cities. f. Explain why the heights of the bars for the relative frequency bar graph for the total are not equal to the sums of the heights for the individual cities. Answers to Check Your Understanding Exercises for Section 2.1 1. a. Aircraft Frequency Twin 9 Single 10 Helicopter 2 Turboprop 5 Jet 4 b. Aircraft Frequency Relative Frequency Twin 9 0.300 Single 10 0.333 Helicopter 2 0.067 Turboprop 5 0.167 Jet 4 0.133 Continued on page 48
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