Image: https://upload.wikimedia.org/wikipedia/commons/thumb/0/09/Dewey_Defeats_Truman.jpg/220px-Dewey_Defeats_Truman.jpg
长久以来，民意调查一直是美国政治活动的一部分，候选人可通过民意调查了解选民的想法，人们则可在下一次选举的数周、数月甚至数年之前就大致看出哪位候选人处于领先地位。
民意调查者认为，如果向足够多的具有代表性的民众提出若干措辞严谨的问题，便可较为准确地得知普通民众的想法。埃尔莫·罗珀（Elmo Roper）、乔治·盖洛普（George Gallup）以及路易斯·哈里斯（Louis Harris）等民意调查的先驱曾大致成功地预测出选举结果。
不过，也有一些不准确的民意调查和预测，比如在1948年总统大选中，《芝加哥论坛报》早早用头版头条宣告“杜威击败杜鲁门”。而内特·希尔沃（Nate Silver）等当代总统选举的民调人员自有一套复杂的民意调查方法。
一份具有代表性的美国选举民调样本包括多少人？这些人的背景又是怎样的？
欲了解更多信息，请参阅链接（中文）：
https://share.america.gov/wp-content/uploads/2016/05/Elections-USA_In-Brief-Series_Chinese_Lo-Res.pdf
Public -opinion polls have long been a part of the U.S. political scene. They help candidates understand what’s on voters’ minds and they give everyone a sense of who’s ahead — or seems to be — weeks, months and even years before the next election.
Pollsters believe that if they ask a sufficiently large and representative sample of the public a number of fairly worded questions, they can determine the views of the general population with a high degree of accuracy. Polling pioneers like Elmo Roper, George Gallup and Louis Harris were generally successful in predicting election results.
However, there are a few cases of inaccurate polling and predictions, such as the Chicago Tribune headline of “Dewey Defeats Truman” in the 1948 Presidential Election. Modern presidential pollsters, such as Nate Silver, have sophisticated polling operations of their own.
How many people and from what backgrounds would make a representative sample of America for an election poll?
To learn more, see (ch)
https://share.america.gov/wp-content/uploads/2016/05/Elections-USA_In-Brief-Series_Chinese_Lo-Res.pdf
