Gigerenzer,G.

Medical doctors tend to think of psychologists as therapists, useful for emotionally disturbed patients, but not for members of their own trade. Research on transparent risk communication is beginning to change that view, however. As a young researcher, I was struck by a study conducted by David Eddy, now Senior Advisor for Health Policy and Management at Kaiser Permanente. He asked American physicians to estimate the probability that a woman had breast cancer given a positive screening mammogram and provided them with the relevant information: a base rate of 1 percent, a sensitivity of 80 percent, and a false-positive rate of 9.6 percent. Approximately 95 out of 100 physicians wrongly reckoned this probability to be around 75 percent, whereas the correct answer is 7.7 percent (Eddy, 1982). Eddy concluded that many physicians make major errors in statistical thinking that threaten the quality of medical care. How could doctors not have known the answer? Even if some of the doctors tested were “mathematically challenged,” they should already have known that only about one in 10 women with a positive screening mammogram has cancer. Mammography is one of the most frequently tested medical procedures, with widely published results about its accuracy. But most doctors don’t have the time to read medical journals, and few women know that a positive mammogram is like an activated car alarm — usually a false call. As a result, millions of women who test positive every year are unnecessarily frightened.

Gigerenzer, G. (2007). Helping physicians understand screening tests will improve health care. Observer, 20, 37-38. (Full text)

Publication year	2007
Document type:	Article
Publication status:	Published
External URL:	http://library.mpib-berlin.mpg.de/ft/gg/GG_Helping_2007.pdf View
Categories:	HealthBusinessProbabilityRisk Communication
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