Displaying Distributions

1
Displaying Distributions Qualitative Variables

• Lecture 14
• Sections 4.3.1 4.3.2
• Fri, Feb 9, 2007

2
Pie Charts

• Pie chart.
• Use the percentage associated with the category
  to compute the central angle of the pie slice.
• E.g., 25 of 360? 90?.
• A pie chart facilitates the comparison of one
  category to the whole.

3
Example

• Meet Pie-Chart Pam.
• Make a pie chart of the political affiliations at
  UNC-Chapel Hill.
• What does the pie chart tell us?
• Is a pie chart an appropriate display of these
  data?

4
Bar Graphs

• Bar graph.
• A bar graph facilitates the comparison of one
  category to another.
• Bar graph of political affiliation.

5
Example

• Pie-Chart Pam also does bar graphs.
• Make a pie chart of the political affiliations at
  UNC-Chapel Hill.
• What does it tell us?
• Is a bar graph an appropriate display of these
  data?

6
Pie Chart Examples

• Where Your Income Tax Money Really Goes
• Major Religions of the World Ranked by Number of
  Adherents
• Warning against using piecharts