1、what is the Definition of a Confidence Interval?

置信区间是特定统计量的不确定性。置信区间通常有误差范围。它告诉你，你有多大的信心，从民意调查或调查的结果，反映出你会发现什么，如果有可能调查整个群体。置信区间与置信水平(confidence levels)有内在联系

2、Confidence Intervals vs. Confidence Levels

信心水平(Confidence Levels)以百分比表示(例如，95%的信心水平)。这意味着，如果你一遍又一遍地重复一个实验或调查，95%的情况下你的结果将与你从人群中得到的结果相匹配(换句话说，你的统计数据将是合理的!)置信区间是你的结果…通常是数字。例如，你调查一群宠物主人，看他们一年买多少罐狗粮。在99%的置信水平上测试统计数据，得到置信区间(200,300)。这意味着你认为他们买的是20美元。

Confidence levels are expressed as a percentage (for example, a 95% confidence level). It means that should you repeat an experiment or survey over and over again, 95 percent of the time your results will match the results you get from a population (in other words, your statistics would be sound!). Confidence intervals are your results…usually numbers. For example, you survey a group of pet owners to see how many cans of dog food they purchase a year. You test your statistics at the 99 percent confidence level and get a confidence interval of (200,300). That means you think they buy between 200 and 300 cans a year. You’re super confident (99% is a very high level!) that your results are sound, statistically.

3、Real Life Examples of Confidence Intervals

2008年盖洛普(Gallup)的一项调查发现，拥有电视可能对健康有益。民意调查的结果表明，信心水平为95% +/-3，也就是说，如果盖洛普用同样的方法反复进行民意调查，95%的情况下，结果会落在公布的结果之内。95%是置信水平，+/-3称为误差范围。在本文的开头，您将看到统计数据(和柱状图)。在本文的末尾，您将看到置信区间。例如，“对于欧洲的数据，我们可以说95%的信心。

A 2008 Gallup survey found that TV ownership may be good for wellbeing. The results from the poll stated that the confidence level was 95% +/-3, which means that if Gallup repeated the poll over and over, using the same techniques, 95% of the time the results would fall within the published results. The 95% is the confidence level and the +/-3 is called a margin of error. At the beginning of the article you’ll see statistics (and bar graphs). At the bottom of the article you’ll see the confidence intervals. For example, “For the European data, one can say with 95% confidence that the true population for wellbeing among those without TVs is between 4.88 and 5.26.” The confidence interval here is “between 4.88 and 5.26“.

美国人口普查局(U.S. Census Bureau)在调查中通常使用90%的置信度。1995年的一项关于贫困人口的调查表明，90%的人对统计数字有信心。这意味着，如果人口普查局用同样的方法重复这项调查，90%的调查结果将落在35534124至37315094名贫困人口之间。所述数字(35 534 124至37 315 094)是置信区间。

The U.S. Census Bureau routinely uses confidence levels of 90% in their surveys. One survey of the number of people in poverty in 1995 stated a confidence level of 90% for the statistics “The number of people in poverty in the United States is 35,534,124 to 37,315,094.” That means if the Census Bureau repeated the survey using the same techniques, 90 percent of the time the results would fall between 35,534,124 and 37,315,094 people in poverty. The stated figure (35,534,124 to 37,315,094) is the confidence interval.