In order to translate measures of relative risk, such as odds ratios or hazard ratios, to the more easily interpretable changes in absolute risk, we need baseline risks: the proportion of people in the ‘unexposed’ group who experience the outcome of interest. This will help make sense of the real magnitude of the risks reported in research and to be able to communicate its relevance to wider audiences.

Unfortunately, baseline risks are not readily obtained for case-control studies: a fairly common design in which people who have experienced the outcome are identified (the cases), and matched to some extent (say…

David Spiegelhalter

Statistician, communicator about evidence, risk, probability, chance, uncertainty, etc. Chair, Winton Centre for Risk and Evidence Communication, Cambridge.

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