The science underlying modern pharmaceuticals gets distorted by commercial considerations. Manufacturers quite naturally seek to present their products favourably, for instance, by highlighting relative risk reduction when absolute risk reduction gives a more accurate picture of a drug’s efficacy. If trials suggest a medication will reduce a patient’s risk of stroke over the next five years from, say, 4 per cent to 3 per cent then the relative risk reduction is an impressive-sounding 25 per cent (the risk reduces by one fourth) but the absolute risk reduction is a measly 1 per cent (one chance in a hundred).
Wednesday, September 02, 2009
Lies, damned lies and statistics
A doctor writing in Online Opinion neatly illustrates a statistical trick used to spin messages, usually fooling journalists into parroting figures that mislead readers. The same trick is used by prohibitionists -- and also swallowed uncritically by lazy journalists.
Dr Andrew Gunn, editor of New Doctor, writes:
Prohibitionists reverse the effect, as noted elsewhere in this blog, typically in alarmist messages about cannabis and psychosis. A 40% increase in risk sounds horrifying but if it's happening among far less than 1% of users it falls into perspective.
They should teach this statistical trick in journalism school.