This is the fifth article of a series on fundamental concepts in biostatistics and research.In this article, the author reviews the fundamental concepts in diagnostic HEMORRHOID OINTMENT testing, prior probability and predictive value, and how they relate to the concept of high-value care.The topics are discussed in common language with a minimum of jargon and mathematics.Emphasis is given to conceptual Eyeliner understanding.A companion article preceding this one focused on sensitivity and specificity.