The Association for Psychological Science’s Observer has an interesting article by Gerd Gigerenzer, on helping physician’s make decisions. Here is an excerpt of his discussion of the relative risk statistic versus the absolute risk statistic:

Another numerical representation that tends to cloud doctors’ minds is relative risk. We read that mammography screening reduces the risk of dying of breast cancer by 25 percent. Many people believe this to mean that the lives of 250 out of 1,000 women are saved, whereas a group of Swiss gynecologists’ interpretations varied between one in 1,000 and 750 in 1,000! How large is the actual benefit? Randomized trials showed that, out of 1,000 women not screened, four died of breast cancer within about 10 years, whereas among those who were screened, three died. Thus, the absolute risk reduction is one out of 1,000 women, or 0.1 percent, whereas the relative risk reduction is 25 percent. In a representative 2006 survey of 1,000 German citizens, I found that hardly anyone understands what the 25 percent means. Other sources of confusion are single-event probabilities and five-year survival rates.