Here is some *light* reading for some of the number juggling (or not) that physicians deal with every day with regard to ordering screening exams/tests for their patients. Being a physician, grasping these numbers is difficult. Realizing the difference between sensitivity, specificity, positive predictive value, and negative predictive value was paramount in many of my medical school lectures. Even then, though, the concepts, as shown in the link, are abstract, obtuse, and not easily accounted for in daily decision making.

Human beings taking care of human beings. There is bound to be some imperfection. Now, if only we could invent mammography@ (i.e., a highly sensitive screening test) and mammography* (i.e., a highly specific confirmation test), we’d be better off. Think for a moment why two tests would be needed.