Relative risk

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Relative risk is the percentage change risk associated with one activity over another - such as "going for a drive" compared to "doing nothing". It is the most common value quoted in the media due to the virtue of it being inevitably the largest and most dramatic value available. Although scientists usually report it as a ratio of probabilities, results are commonly discussed as percentages. On its own, the relative risk of an activity or medical intervention is essentially meaningless, it must be used in conjunction with absolute figures - a 100% increase may sound dramatic, but it can be put in context by saying this is a change from 1 in 100,000 to 2 in 100,000. Furthermore, the reference category matters. A 100% change with one reference group sounds much more impressive than the 50% reduction if the two groups were reversed. To make the value even higher, the popular press usually quote the risk relative to doing nothing, as doing nothing is risk free (sort of) while doing anything at all will change it.

Example

The use and misuse of "relative risk", is best shown with an example - and there are plenty to chose from. For example, one of the many, many headlines that appear on almost every issue of the Daily Mail.[1][2][3]