What's the Denominator? A Lesson on Risk

Mathematics is at the heart of all science and is central to the interpretation of research findings in settings ranging from the clinical application of new medications to personal decisions about acceptable levels of risk. Unfortunately, many Americans, including most students, have a poor grasp of mathematics, and rational risk analysis is one casualty. People who lack the skill of relating one number to another may overreact to relatively minor risks, perceiving certain situations or activities as dangerous when, in fact, they are not. Conversely, these people may disregard real risks. The fear of flying by someone who never wears a seat belt in his car is one example. A variety of psychosocial factors affect how one perceives risk. Likewise, most people view the risk of acute but unlikely illness (e.g., mercury poisoning) as more disturbing than the risk of chronic and common illness (e.g., heart disease or diabetes). This is consistent with one's tendency to evaluate a risk, in part, according to one's perception of "dread." But this is not the whole story. Ignorance about how to analyze the numbers used to describe risk is yet another reason for faulty risk assessment. Many people have never been challenged to answer and internalize the question: What is the risk being compared to? This is a question that teachers can address with their students. This article presents a brief activity which can help students begin to evaluate risk more thoughtfully.