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Med Decis Making. 2005 Jul-Aug;25(4):398-405.

Reducing the influence of anecdotal reasoning on people's health care decisions: is a picture worth a thousand statistics?

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VA Health Services Research & Development Center of Excellence, VA Ann Arbor Healthcare System, Ann Arbor, MI 48109-0429, USA.



People's treatment decisions are often influenced by anecdotal rather than statistical information. This can lead to patients making decisions based on others' experiences rather than on evidence-based medicine.


. To test whether the use of a quiz or pictograph decreases people's reliance on anecdotal information.


. Two cross-sectional survey studies using hypothetical scenarios. Participants read a scenario describing angina and indicated a preference for either bypass surgery or balloon angioplasty. The cure rate of both treatments was presented using prose, a pictograph, a quiz, or a pictograph and quiz combination. Participants read anecdotes from hypothetical patients who described the outcome of their treatment; the number of successful anecdotes was either representative or unrepresentative of the cure rates. Setting and Participants. Prospective jurors at the Philadelphia County Courthouse and travelers at the Detroit-Wayne County Metropolitan Airport. Measurements. Proportion of respondents preferring bypass over balloon angioplasty.


. In study 1, when statistical information was presented in prose, treatment choices were influenced by anecdotes, with 41% of participants choosing bypass when the anecdotes were representative and only 20% choosing it when the anecdotes were unrepresentative (x(2) = 14.40, P < 0.001). When statistics were reinforced with the pictograph and quiz, anecdotes had no significant influence on treatment decisions (38% choosing bypass when anecdotes were representative v. 44% when unrepresentative, x(2) = 1.08, P > 0.20). In study 2, the tradeoff quiz did not reduce the impact of the anecdotes (27% v. 28% choosing bypass after receiving or not receiving the quiz, x(2) < 1, P > 0.20). However, the pictograph significantly reduced the impact of anecdotes, with 27% choosing bypass after receiving no pictograph and 40% choosing bypass after receiving a pictograph (x(2) = 6.44, P < 0.001).


. Presenting statistical information using a pictograph can reduce the undue influence of anecdotal reasoning on treatment choices.

[Indexed for MEDLINE]

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