sampling strategy A directive information that describes how population units will be chosen for sample/data collection in a surveillance activity. Describe how units have been planned to be sampled Sampling at the primary sampling unit (PSU) level Describe the information used to calculate sample size at the PSU level, e.g. the number of PSU in the population (see section 6 also), (between−herd) design prevalence, desired confidence, desired power, sensitivity, specificity. If recommended parameters from international standards are used, indicate the source of such standards (e.g. OIE) Sampling at the secondary sampling unit (SSU) level Describe the information used to calculate sample size at the SSU level, e.g. the number of SSU in the population (see section 6 also), (within−herd) design prevalence, desired confidence, desired power, sensitivity, specificity. https://github.com/SVA-SE/AHSURED/wiki/Description-of-surveillance-items-in-the-checklist https://www.fp7-risksur.eu/terminology/glossary directive information entity