This AOP provides guidance for selecting test items that adequately represent the whole population to be assessed. The document discusses the relative merits of probabilistic and non-probabilistic sample selection and suggests how to determine when to remove samples for testing. This part also indicates where predictive testing shall be required and how the testing requirements can be determined. Operational Imperative statement: This document is relevant to anyone wishing to define the sampling techniques for surveillance or estimate the resources required for a surveillance program.