Helping doctors and patients make sense of health statistics: towards an evidence-based society

Collective statistical illiteracy is the phenomenon that the majority of people do not understand what health statistics mean, or even consistently draw wrong conclusions without noticing. For instance, few are aware that higher survival rates with cancer screening do not imply longer life, or that the statement that mammography screening reduces the risk of dying from breast cancer by 20% in fact means that 1 less woman out of 1,000 will die of breast cancer. I argue that statistical illiteracy (i) is common to patients, journalists, and physicians alike; (ii) is created by nontransparent framing of information that is sometimes an unintentional result of lack of understanding, but can also be an intentional effort to manipulate or persuade people; and (iii) is a consequence of the ongoing lack of efficient training in statistical thinking in the educational system.