l**h
发帖数: 809 | 1 那位高手给说说第二空是多少，包子答谢
A computer file contains marketing data on 50,000 families. For 40,000 of
the families, the file has an entry for family income. For these families,
the average income is $31,000 and the standard deviation is $20,000. For the
other 10,000 families, income information is missing. An economist plans to
take a simple random sample of 625 from the 50,000 families. Many on the
families in the sample will have an income entry in the file. The total of
the incomes of these families w | l**h
发帖数: 809 | 2 自己顶一下，那位给看看
the
to
【在 l**h 的大作中提到】
: 那位高手给说说第二空是多少，包子答谢
: A computer file contains marketing data on 50,000 families. For 40,000 of
: the families, the file has an entry for family income. For these families,
: the average income is $31,000 and the standard deviation is $20,000. For the
: other 10,000 families, income information is missing. An economist plans to
: take a simple random sample of 625 from the 50,000 families. Many on the
: families in the sample will have an income entry in the file. The total of
: the incomes of these families w
| c**********y
发帖数: 4 | 3 我想的可不一定对，但是给其它人提供最初思路吧
我想分析还是得从40000个家庭的数字入手，10000个应该也是同40000个差不多的分布。
现在从50000里挑625，以我的理解，应该会有500个是在这40000里，125在10000里，-- |
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