How does PIAAC select a representative sample of adults?
• Countries that participate in PIAAC must draw a sample of individuals ages 16 to 65 that represent the entire population of adults living in households in the country. Some countries draw their samples from their national registries of all persons in the country; others draw their samples from census data. In the United States, a nationally representative household sample was drawn from the most current Census Bureau population estimates. The U.S. sample design employed by the PIAAC is generally referred to as a four-stage stratified area probability sample. This method involves the selection of (1) primary sampling units (PSUs) consisting of counties or groups of contiguous counties, (2) secondary sampling units (referred to as segments) consisting of area blocks, (3) dwelling units (DUs), and (4) eligible persons (ultimate sampling unit) within DUs. Random selection methods are used, with calculable probabilities of selection at each stage of sampling. This sample design ensures th
