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某地共有1100个居民家庭，高收入和低收入约为100户，余下的1000户收入大致呈现正态分部，高收入与低收入的收入差距大约是400元，若要估计正常收入的1000户的户均收入，以95％的置信水平保证估计误差不超过30元，问样本应抽取多少户才比较合适？

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关键词：统计学 收入差距 置信水平 低收入 高收入 收入差距 统计学 样本

You first need to estimate the standard deviation, which is a quarter of the range, i.e., 400/4=100.

Your sample size should be around (1.96*100/30)^2.

pingguagain 发表于 2014-2-25 04:01
You first need to estimate the standard deviation, which is a quarter of the range, i.e., 400/4=100. ...

thanks a million

pingguagain 发表于 2014-2-25 04:01
You first need to estimate the standard deviation, which is a quarter of the range, i.e., 400/4=100. ...

Why the the standard deviation of income  is 400/4 ?

cicero1314 发表于 2014-2-25 16:36
Why the the standard deviation of income  is 400/4 ?

It is empiricial. Also think about Normal distribution, 95% confidence interval is [ -1.96 s, +1.96s], which length (range) is almost 4s.