Learn in the textbookPopulation and Sampling
DefinitionMultistage sampling (多段抽出) repeats random selection in stages, from large units down to smaller ones, and finally picks individuals or households as the sample.
ExplanationStage 1 picks large units such as municipalities, and each later stage chooses the next units only from within those picked in the stage before. There is no need to build a list of the whole population, and the areas to visit are clustered, which saves effort in nationwide surveys. The trade-off is that each added stage brings its own selection variation, so sampling error tends to grow.
AnalogyIt is like checking stock in a large warehouse: first pick a few shelves, then pick boxes from those shelves, and finally inspect the items inside the boxes.