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Applied Mathematic
(Preliminary General 1)
Misleading
Graphs
Stage 6 - Year 11
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©G Dear 2010 – Not to be sold/Free to use

2. In the business world we don’t want to create misleading graphs
Three types (of many) are: 50 60 70 80
1. Displaced Axes.
Does not start at zero.
2. Exaggerated Area or Vol. 10 20 30
Size exaggerates the difference. 10
100
1000
3. Displaced Axes.
Axes are irregularly numbered.
End of
Slide 2

3. The increase in price was not as big as it appeared to be.
Misleading Graphs
Displaced Axes
Massive Increase In
House Prices this Year
82 000
80 000
60 000
Average House Price
81 000
Average House Price
40 000
80 000
20 000
1998
1999
1998
1999
Year
Year
The increase in price was not as big as it appeared to be.
End of
Slide 3

4. Misleading Graphs Displaced Axes
1000
1000
995
900
990
800
985
700
980
600
Number of Votes
Number of Votes
975
500
970
400
965
300
960
200
955
100
950
Pizza
Hot Dogs
Hamburgers
Pizza
Hot Dogs
Hamburgers
Favourite Food
Favourite Food
The number of votes appears significantly here.
The number of votes appears not so significantly here.
End of
Slide 4

5. Misleading Graphs Exaggerated use of Area or Volume.
Number of
Singles Sold
Number of Singles Sold
1995
1996
1997
1998
1998
1997
1996
1995
The Brown column looks bigger than the purple column
But is it?
End of
Slide 5

6. The Exaggerated use of Area or Volume.
Misleading Graphs
The Exaggerated use of Area or Volume.
Key: 50
Key: 50
Dog:
Cat:
Horse:
This is bad.
The various sized pictures distorts the graph.
Dog:
Cat:
This is much better
Horse:
All pictures must be
the about the same size.
(Area)
End of
Slide 6

7. Exaggerated use of Area or Volume.
Misleading Graphs
Exaggerated use of Area or Volume.
Sales at Gerry’s Milkbar have doubled from 2007 to 2008.
2007
2008
The 2008 volume is eight times bigger than the 2007 volume.
End of
Slide 7

8. Source: www.scribd.com/doc/19047168/19-Misleading-Graphs
Irregular Scale Axes
Source:
1993, 1996 and 1998 are missing.
End of
Slide 8

9. Source: www.scribd.com/doc/19047168/19-Misleading-Graphs
Irregular Scale Axes
Source:
1993, 1996 and 1998 are added.
End of
Show 9