used to cut down on travelling expences; The survey universe (country?) is divided into areas and a smaller sample of these is selected at random; these are then broken down into even smaller samples and so on; eventually selecting a random sample to be interviewed from the smallest groups.
SAMPLING; MULTISTAGE
Meaning of SAMPLING; MULTISTAGE in English
Raynet Business and Marketing English glossary. Английский глоссарий компании Raynet Business and Marketing . 2012