CALCULATED RISKS: How to Know When Numbers Deceive You

If a woman aged 40 to 50 has breast cancer, nine times out of 10 it will show up on a mammogram. On the other hand, nine out of 10 suspicious mammograms turn out not to be cancer. Confused? So are many people who seek certainty through numbers, says Gigerenzer, a statistician and behavioral scientist. His book is a successful attempt to help "innumerates" (those who don't understand statistics), offering case studies of people who desperately need to understand statistics, including those working in AIDS counseling, DNA fingerprinting and domestic violence cases. Gigerenzer deftly intersperses math lessons—explaining concepts like frequency and risk in layperson's terms—with real-life stories involving doctors and detectives. One of his main themes is that even well-meaning, statistically astute professionals may be unable to communicate concepts such as statistical risk to innumerates. (He tells the true story of a psychiatrist who prescribes Prozac to a patient and warns him about potential side effects, saying, "You have a 30 to 50 percent chance of developing a sexual problem." The patient worries that in anywhere from 30% to 50% of all his sexual encounters, he is going to have performance problems. But what the doctor really meant is that for every 10 people who take Prozac, three to five may experience sexual side effects, and many have no sexual side effects at all.) All innumerates—buyers, sellers, students, professors, doctors, patients, lawyers and their clients, politicians, voters, writers and readers—have something to learn from Gigerenzer's quirky—yet understandable—book. Agent, John Brockman. (June)

Forecast: What's the probability of Gigerenzer's work becoming a bestseller? Let's just say it's hard to imagine a book about statistics flying off the shelves (although John Allen Paulos's Innumeracy was a bestseller just two years back). Still, if Gigerenzer gets enough publicity—his book has an exposé, "here's what those statistics really mean" edge to it—audiences might respond.