Questions 20-30

　　A survey is a study, generally in the form of an interview or a questionnaire, that provides

　　information concerning how people think and act. In the United States, the best-known

　　surveys are the Gallup poll and the Harris poll. As anyone who watches the news during Line

　　campaigns presidential knows, these polls have become an important part of political life in

　　(5) the United States.

　　North Americans are familiar with the many "person on the street? interviews on local

　　television news shows. While such interviews can be highly entertaining, they are not

　　necessarily an accurate indication of public opinion. First, they reflect the opinions of only

　　those people who appear at a certain location. Thus, such samples can be biased in favor

　　(10) of commuters, middle-class shoppers, or factory workers, depending On which area the

　　newspeople select. Second, television interviews tend to attract outgoing people who are

　　willing to appear on the air, while they frighten away others who may feel intimidated by

　　a camera. A survey must be based on a precise, representative sampling if it is to genuinely

　　reflect a broad range of the population.

　　(15) In preparing to conduct a survey, sociologists must exercise great care in the wording

　　of questions. An effective survey question must be simple and clear enough for people to

　　understand it. It must also be specific enough so that there are no problems in interpreting

　　the results. Even questions that are less structured must be carefully phrased in order to elicit

　　the type of information desired. Surveys can be indispensable sources of information, but

　　(20) only if the sampling is done properly and the questions are worded accurately.

　　There are two main forms of surveys: the interview and the questionnaire. Each of these

　　forms of survey research has its advantages. An interviewer can obtain a high response rate

　　because people find it more difficult to turn down a personal request for an interview than

　　to throw away a written questionnaire. In addition, an interviewer can go beyond written

　　(25) questions and probe for a subject's underlying feelings and reasons. However, questionnaires

　　have the advantage of being cheaper and more consistent.

　　20. What does the passage mainly discuss?

　　(A) The history of surveys in North America

　　(B) The principles of conducting surveys

　　(C) Problems associated with interpreting surveys

　　(D) The importance of polls in American political life

　　21. The word "they" in line 8 refers to

　　(A) North Americans

　　(B) news shows

　　(C) interviews

　　(D) opinions

(实习编辑：武勐勐)