The discriminatory power of diagnostic information can be measured by the levels and differences between two inverse conditional probability assessments, and , one for each possible diagnostic test result. This interactive Demonstration creates a graphical depiction of the inverse probabilities and as functions of the underlying sensitivity, specificity, and base rate inputs. A natural frequency representation of the full joint probability distribution over the random variables (, ) is provided in a truth table format above the graph, where the column entries are frequency counts or "cases" in a hypothetical population of a fixed size.