SECTION 2.2 More Graphs and Displays 61 A data set that is composed of quantitative entries taken at regular intervals over a period of time is called a time series. For instance, the amount of precipitation measured each day for one month is a time series. You can use a time series chart to graph a time series. Constructing a Time Series Chart The table lists the numbers of burglaries (in millions) and robberies (in thousands) in the United States for the years 2009 through 2019. Construct a time series chart for the number of burglaries. Describe any trends. (Source: Federal Bureau of Investigation, Crime in the United States) Year Burglaries (in millions) Robberies (in thousands) 2009 2.20 409 2010 2.17 369 2011 2.19 355 2012 2.11 355 2013 1.93 345 2014 1.71 323 2015 1.59 328 2016 1.52 333 2017 1.40 321 2018 1.24 281 2019 1.12 268 SOLUTION Let the horizontal axis represent the years and let the vertical axis represent the numbers of burglaries (in millions). Then plot the paired data and connect them with line segments Year Burglaries (in millions) Burglaries 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 0.5 1.0 1.5 2.0 2.5 3.0 Interpretation The time series chart shows that the number of burglaries remained about the same until 2011 and then decreased through 2019. TRY IT YOURSELF 7 Use the table in Example 7 to construct a time series chart for the number of robberies for the years 2009 through 2019. Describe any trends. Answer: Page A36 See Minitab and TI-84 Plus steps on pages 124 and 125. EXAMPLE 7
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