(68) Visualizing very small risks

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Some risk communication situations require helping people to visualize just how rare very rare events are. A common example occurs in prenatal genetic testing. If a couple has no other risk factors, the baseline risk of genetic diseases such as Down Syndrome is often much smaller than even 1 in 1000 (0.1%). Visually showing this ratio is challenging.

What’s special about this image?

This multi-bar graphic uses reference bars at 100%, 50%, 10%, and 1% to make the smallness of the 0.08% risk level much clearer.

Please note the European convention of writing 0,08% rather than the American convention of 0.08%. The graphic was tested in this way (in error), but should be corrected before using it with American audiences.
  • My goal
  • Awareness of risk
  • Raise or lower concern
  • Details or gist?
  • Verbatim recall
  • Data I have
  • Risk estimate
  • Test result
  • Health conditions
  • Down syndrome
  • Graphic type
  • Callout
  • Bar graph