Recent research in health decision making has shown that many patients, even those with a college education, have difficulties grasping a host of numerical concepts, including percentages and probabilities. Yet, basic numeracy and graph literacy are essential for understanding information relevant to making decisions about health, such as the incidence and prevalence of different diseases, risk reductions from medical screenings and treatments, and risk increases from side effects of treatments and unhealthy behaviors. Patients who have problems understanding such numerical concepts are...