误差范围

误差范围表达了统计结果中的随机波动的大小。这可以视为同样的问卷调查进行多次，其报告的百分比的变化的衡量。误差范围越大，该调查得到的百分比接近“真实”值（也就是在整个样本空间中的百分比）的可能性越低。

The top portion of this graphic depicts probability densities that show the relative likelihood that the "true" percentage is in a particular area given a reported percentage of 50%. The bottom portion of this graphic shows the margin of error, the corresponding zone of 99 % confidence. In other words, one is 99% sure that the "true" percentage is in this region given a poll with the sample size shown to the right. The larger the sample is, the smaller the margin of error is. If lower standards of confidence (95 or 90 %) are used, the margins of error will be smaller (by 24 or 36%, respectively) for the same sample sizes.

误差范围可以通过一次抽样调查得到的每个数字进行计算，除非所进行的是一次非概率抽样。对于以百分比表达的结果，经常可以计算一个最大误差范围，它适用于该调查的所有结果（至少所有基于整个采样的结果）。有时最大误差范围可以直接从采样的大小（回答问卷者的数量）计算。

误差范围通常在三个可信度上给出；99%，95%和90%。99%这个级别是最保守的，而90%的级别是最不保守的。95%的级别最为常用。如果可信度为95％，则整个样本空间的“真实”百分比有95％的可能处于一个问卷的结果的误差范围内。等价的说，误差范围就是95％可信区间的半径。

注意误差范围只考虑随机采样误差。它不考虑潜在的其它误差源，例如问题中的偏向性，没有被调查到的群体所带来的偏差，拒绝回答或者撒谎的人带来的误差，错误记数或者计算带来的偏差，等等。

参考

Sudman, Seymour & Bradburn, Norman (1982). Asking Questions: A Practical Guide to Questionnaire Design. San Francisco: Jossey Bass.

外部链接

Stokes, Lynne; Tom Belin. (PDF). What is a Survey?. Survey Research Methods Section, American Statistical Association: 63–67. 2004 [2006-05-31]. （原始内容 (PDF)存档于2013-03-12）（英语）.
Braiker, Brian. . MSNBC. October 2, 2004 [2006-06-13]. （原始内容存档于2006-06-14）.
(新闻稿). Newsweek. 2004-10-02 [2006-05-31]. （原始内容存档于2005-08-26）.
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