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- UID
- 223277
- 帖子
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- 注册时间
- 2011-7-11
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- 2013-10-9
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it's very easy if you think of it.
what's the mean age in this forum?
what's the standard deviation?
If you want to be 95% sure that a randomly sampled person, is younger than x, which number would you choose?
mu + 1.65*sd
mu + 1.65*sd/sqrt(number of persons writing here) |
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发表于 2011-7-13 16:20
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