Probability of Detection

Probability of detection (POD) evaluation is a commonly used method of quantifying the reliability of an inspection.  Inspections in practice have multiple factors which affect the detectability of flaws (e.g. human factors, uncertainty in the geometry of the part under test, or sensor/instrument noise).  A POD study seeks to quantify the effect of these factors by answering the question:

What is the largest flaw that could be

missed when this inspection is

implemented in production?

POD provides an answer to this question by assessing the probability of detecting a flaw as a function of some defining characteristic (typically flaw length or depth).  Along with estimating false call rate, POD has been successfully implemented in multiple industries as the primary method of reliability quantification for NDI inspections.  This article is intended to introduce key aspects of POD that will help in understanding the scope and limitations of a POD study.