The cluster sample method is most often used because, in the initial stages of emergencies, people are rarely living in a structured pattern. 分组抽样方法是最常用的，因为在紧急情况的初期，人们很少住在有组织的环境中。
structured英英释义
Adjective:
having definite and highly organized structure;
"a structured environment"
resembling a living organism in organization or development;
