two-stage sampling - a type of sampling based on basic and secondary units. The basic units (e.g., states of the United States) are first sampled, then subsampled with respect to their secondary or subordinate units (e.g., counties). ;
дс тдрлими цюлютдажкию дроемжки аиакиохдйис лидр
http://www.harcourt.com/dictionary/def/1/0/7/0/10701400.html;
