This display tries to help patients compare their current risk withoutscreening tests versus their reduced risk if they have screening tests. In particular, it aims to help patients understand the absolute size of the possible risk reduction.
This dot matrix display uses 1,000 dots to represent the probability space (each dot = 0.1%). As a result, it is easy to count the dots to see each of the 7 people out of 1,000 (0.7%) whose risk is reduced because of cancer screening tests.
Note that this display works well for small risks that are larger than 0.1% but would have problems visually grouping and labeling risks larger than 3%.
In our testing, this image helped people more accurately report the risk with screening tests and the risk difference for screening vs non-screening. It performed equally well on risk perceptions as other accurate graphics do. We recommend this image.