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How to Avoid Some Common Graphical Mistakes London October 1, 2012 Copyright © 2012, Naomi B. Robbins.

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Presentation on theme: "How to Avoid Some Common Graphical Mistakes London October 1, 2012 Copyright © 2012, Naomi B. Robbins."— Presentation transcript:

1 How to Avoid Some Common Graphical Mistakes London October 1, 2012 Copyright © 2012, Naomi B. Robbins

2 Graphical Mistakes  Misleading the audience  Not making the data stand out  Problems with tick marks and labels  Two useful graphical methods

3 Graphical Mistakes  Misleading the audience  Not making the data stand out  Problems with tick marks and labels  Two useful graphical methods

4 Avoid misleading the audience Equally spaced tick marks for unequal intervals Bar graphs with no zero Comparisons with different scales Figures not to scale

5 Evenly spaced tick marks for uneven intervals

6 Justice Dep’t version

7 Comparison

8 Another example

9 Uneven ticks for same intervals

10 Actuarial: Time handled correctly

11 Bar charts with no zero Source:http://www.washingtonpost.com/blogs/ezra-klein/wp/2012/09/06/bill-clintons-speech-in-graphs/

12 Novelty before accuracy

13 Graphical Mistakes  Misleading the audience  Not making the data stand out  Problems with tick marks and labels  Two useful graphical methods

14 Make the data stand out Factors that keep data from standing out: Clutter –Too many percent signs –Too many trailing zeros –Unnecessary dimensions Lack of contrast for model or data Graphical elements hide data

15 USA Today – 4 October 2006

16 Too many percent signs

17 Percent Signs Removed

18 Before and after

19 Too many zeros

20 Eliminate unnecessary dimensions

21 Excel: 3-D bar chart

22 Same data in two dimensions

23 Not making the data (or model) stand out

24 Colors interchanged

25 Before and after

26 Data and axis labels conflict

27 Visual clarity not preserved under reproduction Most slides were yellow on navy so the handouts had the colors inverted. The figure on the right had a white background on the screen.

28 Graphical Mistakes  Misleading the audience  Not making the data stand out  Problems with tick marks and labels  Two useful graphical methods

29 Problems with tick marks and labels Too many labels Tick marks not at sensible numbers Labels hidden by grid lines or axes Labels not proofread

30 Too many labels

31 Another too many labels

32 Tick marks at unreasonable values

33 Reasonable values depend on variable

34 Labels hidden

35 Graph not proofread

36 Graphical Mistakes  Misleading the audience  Not making the data stand out  Problems with tick marks and labels  Two useful graphical methods

37 Useful graphical methods Dot plots Trellis graphics

38 Bar plot of revenues

39 Bar and dot plots of revenues

40 Dot plot of profits

41 Dot plot of profits and superposed plots

42 Before: Multiple pie charts Source: Visualization by Brown et al.

43 Before: Divided bar chart

44 After: Trellis display

45 Comparison

46 For more information: Robbins, Naomi B. Creating More Effective Graphs blogs.forbes.com/naomirobbins


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