84 Chapter 2 Graphical Summaries of Data Year Digital Physical 2004 143.9 814.1 2005 383.1 748.7 2006 625.3 648.2 2007 868.4 543.9 2008 1112.3 401.8 Source: Recording Industry Association of America a. Construct a time-series plot for digital sales. On the same axes, construct a time-series plot for physical sales. b. Describe the trends in sales for digital and physical music formats. 14. More music: Refer to Exercise 13. Although physical formats sell fewer units than digital formats, their retail value is higher— CDs typically sell for $15 or more, while a download single typically costs a dollar or less. The following table presents the total number of music units, in millions, sold in each year from 2004 through 2008, and the total retail value, in millions of dollars, of the sold units. Year Units Sold Retail Value 2004 958.0 12,345 2005 1301.8 12,296 2006 1588.5 11,758 2007 1774.3 10,372 2008 1852.5 8,480 Source: Recording Industry Association of America a. Construct a time-series plot for units sold. b. Construct a time-series plot for total retail value. c. Explain why the total retail value has been decreasing while the total units sold has been increasing. 15. Rising birth rate: The following time-series plots both present the number of births per 1000 women aged 15–44 for the years 2000–2008. Which statement is more accurate? Explain your reasoning. (i) The birth rate rose dramatically between 2001 and 2007. (ii) The birth rate rose slightly between 2001 and 2007. 2000 2001 2002 2003 2004 2005 2006 2007 2008 70 69 68 67 66 65 64 Births per 1000 Women Aged 15 to 44 2000 2001 2002 2003 2004 2005 2006 2007 2008 70 60 50 40 30 20 10 0 Births per 1000 Women Aged 15 to 44 Source: Pew Research Center Write About It 1. Explain why the frequency bar graph and the relative frequency bar graph for a data set have a similar appearance. 2. In what ways do frequency distributions for qualitative data differ from those for quantitative data? 3. Provide an example of a data set whose histogram you would expect to be skewed to the right. Explain why you would expect the histogram to be skewed to the right. 4. Time-series data are discrete when observations are made at regularly spaced time intervals. The time-series data sets in this section are all discrete. Time-series data are continuous when there are observations at extremely closely spaced intervals that are connected to provide values at every instant of time. An example of continuous time-series data is an electrocardiogram. Provide some examples of time-series data that are discrete and some that are continuous. 5. Find examples of graphs in newspapers, magazines, or on the Internet that are misleading in some way. Explain how they are misleading. Then find some that present accurate comparisons and explain why you believe they are accurate.
navidi_monk_essential_statistics_1e_ch1_3
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