58 CHAPTER 2 Descriptive Statistics Graphing Qualitative Data Sets Pie charts provide a convenient way to present qualitative data graphically as percents of a whole. A pie chart is a circle that is divided into sectors that represent categories. The area of each sector is proportional to the frequency of each category. In most cases, you will be interpreting a pie chart or constructing one using technology. Example 4 shows how to construct a pie chart by hand. Constructing a Pie Chart The number of earned degrees conferred (in thousands) in 2019 are shown in the table at the right. Use a pie chart to organize the data. (Source: U.S. National Center for Education Statistics) SOLUTION Begin by finding the relative frequency, or percent, of each category. Then construct the pie chart using the central angle that corresponds to each category. To find the central angle, multiply 360° by the category’s relative frequency. For instance, the central angle for associate’s degrees is 360°(0.255) ≈ 91.8°. Type of degree f Relative frequency Angle Associate’s 1037 0.255 91.8° Bachelor’s 2013 0.494 177.8° Master’s 834 0.205 73.8° Doctoral 188 0.046 16.6° Earned Degrees Conferred in 2019 Doctoral 4.6% Bachelor’s 49.4% Associate’s 25.5% Master’s 20.5% Interpretation From the pie chart, you can see that almost one half of the degrees conferred in 2019 were bachelor’s degrees. TRY IT YOURSELF 4 The number of earned degrees conferred (in thousands) in 2010 are shown in the table. Use a pie chart to organize the data. Compare the 2010 data with the 2019 data. (Source: U.S. National Center for Education Statistics) Earned Degrees Conferred in 2010 Type of degree Number (in thousands) Associate’s 849 Bachelor’s 1650 Master’s 693 Doctoral 159 Answer: Page A36 You can use technology to construct a pie chart. For instance, an Excel pie chart for the degrees conferred in 2019 is shown at the left. EXAMPLE 4 EXCEL Associate's 25.5% Bachelor's 49.4% Master's 20.5% Doctoral 4.6% Degrees Conferred in 2019 Earned Degrees Conferred in 2019 Type of degree Number (in thousands) Associate’s 1037 Bachelor’s 2013 Master’s 834 Doctoral 188
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