Thứ Bảy, ngày 27 tháng 12 năm 2008

Seeing Through Statistics (1): Case Study 3.1

Khi thực hiện một cuộc khảo sát, cần nhớ rằng kết quả khảo sát phụ thuộc rất nhiều vào kỹ thuật và phương pháp khảo sát. Hãy đọc Case sau đây và rút ra kết luận cho chính bạn. Và hãy liên hệ với 7 pitfalls đã nêu trong blog này.

No Opinion of Your Own: Let Politics Decide
(Source: Morin 10-16 April 1995, p. 36)

This is an exellent example of how people will respond to survey questions, even they do not know about the issues, and how the wording of questions can influence responses. In 1995, the Washington Post decided to expand on a 1978 poll taken in Cincinnatti, Ohio, in which people were asked whether they "favoured or opposed repealing the 1975 Public Affairs Act." There was no such act, but about one third of the respondents expressed an opinion about it.

In February 1995, the Washington Post added this fictitious question to its weekly poll of 1000 randomly selected respondents: "Some people say the 1975 Public Affairs Act should be repealed. Do you agree or disagree that it should be repealed?" Almost half of the sample (43%) expressed an opinion, with 24% agreeing that it should be repealed and 19% disagreeing. The Post then tried another trick that produced even more disturbing results. This time, they polled two separate groups of 500 randomly selected adults. The first group was asked: "President Clinton [a Democrat] said that the 1975 Public Affairs Act should be repealed. Do you agree or disagree?" (còn tiếp)

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