Presidential candidates use them to persuade voters, drug companies use them to sell their products, and the media spin them in all kinds of ways, but nobody - candidates, reporters, let alone health consumers - understands them. Health statistics fill today's information environment, but even most doctors, who must make daily decisions and recommendations based on numerical data - for instance, to calculate the risks of a certain drug or surgical intervention, or to inform a patient of the possible benefits versus harms of cancer screening - lack the basic statistical literacy they require to make such decisions effectively.