FIGURE 2-1 Distributions of eye pressure readings in a diagnostic test for glaucoma.

SOURCE: Swets, Dawes, and Monahan (2000). Copyright, John Swets; used by permission.

NOTE: The left panel shows the overlap between the distributions of eye pressures for people who are actually healthy and who actually have glaucoma. The right panel shows the same distributions (glaucoma above, healthy below) together with the consequences of using a pressure of 20 as a diagnostic threshold.