Background Information One of the best- known is the Gallup Poll(盖洛普民测 yo)-a poll of public opinion on a major political or social issue, developed by george H. Gallup, an American statistician. Two methods of sampling are; practised by the polls, random( P NL)and quota sampling. The former consists in selecting persons to be interviewed at random. Quota(sE21) sampling involves selecting a sample of people which is representative of the population in terms of age, occupation, sex, region and so onBackground Information One of the best-known is the Gallup Poll (盖洛普民测 验) — a poll of public opinion on a major political or social issue, developed by George H. Gallup, an American statistician. Two methods of sampling are; practised by the Polls, random (随机)and quota sampling. The former consists in selecting persons to be interviewed at random. Quota（限额）sampling involves selecting a sample of people which is representative of the population in terms of age, occupation, sex, region and so on