This Problem is based on work published in: https://doi.org/10.1098/rsos.201721
Probabilistic information can be represented numerically in different ways, and research has shown that these different formats can affect the perception of likelihoods as well as affecting the ease with which people can make mental comparisons and manipulations of the information [1-5. In the case of people’s risk of dying should they catch COVID-19, the probabilities being represented are often going to be very small (down to around 1 in 10,000 chance of dying), but also fall along a very wide range (up to 25% chance), depending on risk factors, which presents a particular challenge. Common formats include percentages (e.g. 0.5%), natural frequencies (e.g. 5 in 1000), and ‘1 in X’ (e.g. 1 in 200), each of which may have different effects on people’s comprehension and perception of the risk. It is clear that communicators would want to aim for high comprehension (which could be measured as both gist and verbatim), but there is no such thing as a ‘correct’ absolute perception of the risk – although communicators should be aware of the differences that the different formats make to perception.
1. Pighin S, Savadori L, Barilli E, Cremonesi L, Ferrari M, Bonnefon JF. 2011 The 1-in-X effect on the subjective assessment of medical probabilities. Med. Decis. Mak. 31, 721–729. (doi:10.1177/0272989X11403490)
2. Denes-Raj V, Epstein S, Cole J. 1995 The generality of the ratio-bias phenomenon. Pers. Soc. Psychol. Bull. 21, 1083–1092. (doi:10.1177/ 01461672952110009)
3. Siegrist M, Orlow P, Keller C. 2008 The effect of graphical and numerical presentation of hypothetical prenatal diagnosis results on risk perception. Med. Decis. Mak. 28, 567–574. (doi:10.1177/0272989X08315237)
4. Woloshin S, Schwartz LM. 2011 Communicating data about the benefits and harms of treatment: a randomized trial. Ann. Intern. Med. 155, 87–96. (doi:10.7326/0003-4819-155-2- 201107190-00004)
5. Peters E, Hart PS, Fraenkel L. 2011 Informing patients: the influence of numeracy, framing, and format of side effect information on risk perceptions. Med. Decis. Mak. 31, 432–436. (doi:10.1177/0272989X10391672)