BMJ  2003;327:868 (11 October), doi:10.1136/bmj.327.7419.868-a

Letter

Women need better information on routine mammography

Framing is important in presenting risk information

The first 150 words of the full text of this article appear below.

EDITOR—Thornton et al argue that women need better information on breast screening.1 A great deal of evidence is available on how risk should be presented to facilitate understanding.2

Absolute risks should be given more prominence than relative risks. The effects of the decision over the individual's lifetime should be presented rather than the effects in the next few years.

The way information is framed also influences the decisions people reach. Reductions in losses (such as "screening decreases mortality from 6% to 4%") are more persuasive than increases in gains (such as "screening increases survival from 94% to 96%").

Unless our aim is to manipulate, the influence of framing should be minimised by presenting risks of both gains (survival) and losses (mortality). People tend to understand data more easily if they are presented in the form of integers (3 in 10 people) rather than probabilities (30% of people). Any . . . [Full text of this article]

Tom P Marshall, lecturer in public health

University of Birmingham, Birmingham B15 2TT t.p.marshall@bham.ac.uk


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