sampling error
noun/ˈsɑːmplɪŋ erə(r)/
/ˈsæmplɪŋ erər/
(statistics)- a situation in which a set of results or figures does not show a true situation, because the group of people or things it was based on was not typical of a wider group
采样误差（所抽样本不具备代表性）