Annex 3: Risk communication, signal words and information design
Right Decision Service implementation guide
Risk communication examines the impact of alternative formats for risk information, for example a percentage (10%), a figure between 0 and 1 (eg. 0.1) and real numbers such as “1 in 10” or “100 in every 1000”. Graphical and diagrammatic formats such as an array of 100 faces in which 10 are shaded can also be used. A repeated finding from many studies is that humans find it almost impossible to reason with figures from 0-1, very hard with percentages but much easier with real number such as 100 in 1000. Some graphical formats are also useful [Gigerenzer 2003]
Signal words are words such as “Caution”, “Alert”, “Warning” or “Danger”, often displayed in colour, with or without exclamation marks and a triangular background like a road sign. While it is important not to overuse such methods, certain signal words are useful to indicate high priority messages on a crowded, colourful patient record screen [Wogalter 1997]. The use of colour can also be helpful here [Braun 1995].
Information design is the branch of psychology that investigates how to format information so that people can find it fast and interpret it without error. It uses insights from empirical research to inform the layout and formatting of text, tables, graphs, maps and other information formats. We have previously summarised the key insights from the discipline and their implications for the design of electronic patient records in a series of 4 Lancet articles [Wyatt 1998, Nygren 1998, Wright 1998, Powsner 1998]. Some specific insights from empirical studies of text formatting are shown in the Box.
Box: Illustration of the impact of various text formatting modifications on text legibility. Redrawn from Wyatt et al, Lancet 1998
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As font legibility declines, reading slows and people give more attention to the words and less to meaning. |
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Italic text and bold text are less legible than plain text. |
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Printing white text on a shaded or black background makes text less legible, unless a bolder typeface is used. |
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EXTENSIVE USE OF CAPITAL LETTERS SLOWS DOWN READING - Road Signs use Capital and Small Letters. |
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Underlining obscures punctuation such as commas and colons; parts of the letters g, j, p, q, and y are also obscured, reducing legibility. |
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Depending on the background colour some colours, such as red, may be less legible than other colours, such as blue. |
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Especially when there are many long words or circumlocutions, double justification reduces legibility and reading speed compared to unjustified text of the same font size. |
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For a given size of font, short lines or long lines with too many words are more difficult to read than lines of about 10 words. |
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Cramming lines of text close together so there is no space between them confuses the eye, reduces legibility and slows reading, making errors more likely. |