Disclosure avoidance refers to the efforts made to de-identify the data in order to reduce the risk of disclosure of personally identifiable information (PII). A choice of the appropriate de-identification strategy (also referred to as disclosure limitation method) depends on the nature of the data release, the level of protection offered by a specific method, and the usefulness of the resulting data product. The two major types of data release are aggregated data (such as tables showing numbers of enrolled students by race, age, and sex) and microdata (such as individual-level student assessment results by grade and school). Several acceptable de-identification methods exist for each type of data (see disclosure limitation method for more details).
Additional information is available in the PTAC publication Data De-identification: An Overview of Basic Terms.