Sociology 220

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# Sociology 220 - PowerPoint PPT Presentation

Sociology 220 Feb 13, 2009 Prof. Brines MGH 231 Making Sense of Charts, Figures, and Graphs Pie chart Rare in research Common in media Hard to compare wedges (different orientations) Can’t show order Restrict to nominal variables An Unhelpful Pie Chart Pie Charts in politics

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Feb 13, 2009

Prof. Brines

MGH 231

### Making Sense of Charts, Figures, and Graphs

Pie chart

• Rare in research
• Common in media
• Hard to compare wedges (different orientations)
• Can’t show order
• Restrict to nominal variables

Pie Charts in politics

• Federal budget, from the website of the War Resisters’ League
• Redrawn

Bar chart(column chart)

• In research,more common than pie
• Can show order
• Appropriate for ordinal and interval
• (as well as nominal)
• Easy to compare vertical distances

Axis distortion

• Start vertical above zero
• Exaggerates all differences
• Similar distortion:
• Break vertical axis

Line chart(frequency polygon)

• Common in research
• Can show order
• Appropriate for ordinal and interval variables

Bar vs. line: similarities

• Bar and line charts almost equivalent
• Connect tops
• remove bottoms
• You get a line chart!

Bar vs. line: Differences

• Line eases comparison of groups

Histograms

• Like bar chart, except
• Variable typically continuous
• Bars touch
• usually
• Horizontal can represent equal class intervals (“bins”)
• Bin shown by center value (e.g. 35.0)
• Or by ends of class interval (e.g. 33.75-36.25)

Axis distortion in business

• NASDAQ stock index, reported by Yahoo!
• Redrawn