© Keith Vander Linden, 2005

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Graphs and Charts

● Quantitative data can frequently be illustrated in a compelling way using charts and graphs.– see www.gapminder.org for fascinating,

interactive charts

● Spreadsheet systems usually provide graphing and charting capabilities.

● Here are some examples.

© Keith Vander Linden, 2005

© Keith Vander Linden, 2005

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Bar chart of same data

© Keith Vander Linden, 2005

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Pie chart of same data

© Keith Vander Linden, 2005

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image from VDQI, 1983

© Keith Vander Linden, 2005

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Chart Types● Pie charts

– proportional relationships

● Column/bar charts– relative numeric information– (rather than percentages)

● Line charts– change in values over time

● Maps– geographical information– spatial relationships

Financial A id; $20.8

Food; $6.0

B enefits;

$15.6 S alaries;

$35.3

Other; $23.5

Calvin Expenditures, 2003-2004

Bush Kerry Nader Badnarik Cobb Peroutka Brown

0%

10%

20%

30%

40%

50%

60%

48%51%

1% 0% 0% 0% 0%

2004 Election Voting Percentages - Michigan

Candidate

Pe

rce

nta

ge

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

3,7003,8003,9004,0004,1004,2004,3004,400

College Enrollments

Year

En

roll

men

t

© Keith Vander Linden, 2005

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Graph/Chart Issues

● Data values can, however, be obscured or misrepresented using charts.

● Here are some examples.

© Keith Vander Linden, 2005

© Keith Vander Linden, 2005

© Keith Vander Linden, 2005

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image from VDQI, 1983

© Keith Vander Linden, 2005

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image from VDQI, 1983

© Keith Vander Linden, 2005

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image from VDQI, 1983

© Keith Vander Linden, 2005

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Lying graphics cheapen the graphical art everywhere … When a chart on television lies, it lies millions of times over; when a New York Times chart lies, it lies 900,000 times over to a great many important and influential readers. VDQI, p. 53-79

Edward Tufte (1940-) VDQI, 1983

images from www.edwardtufte.com, Oct., 2004

© Keith Vander Linden, 2005

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from Calvin College Chimes, Oct. 6, 2000

© Keith Vander Linden, 2005

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image from Exploring Microsoft Excel 97, Grauer & Barber, 1998

Calvin20%

Hope25%

Kalamazoo30%

Wheaton25%

© Keith Vander Linden, 2005

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image from Exploring Microsoft Excel 97, Grauer & Barber, 1998

2002 2003 2004 2005$0

$10

$20

$30

$40

$50

MyCompany.com

profit

sales

Year

Am

ou

nt

© Keith Vander Linden, 2005

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Using Charts/Graphs Properly

● Decide what you want to present.● Present it accurately and unambiguously.

– Let the graphic values/change accurately depict the data values/change.

– Clearly label all relevant details.– Don’t graphically mix dissimilar elements.– Use the right type of graph.– Don’t add “chartjunk”.

© Keith Vander Linden, 2005

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Technology and Lying● It is as easy to lie or mislead with

technology.

● “When he lies, he speaks his native language, for he is a liar and the father of lies.” - John 8:44

What’s theBig Idea