三道数学题，有空帮我看看啊，没想明白

jessicaddq · 发表于 2010-3-8 18:17:18

LZ能把第三题英文原题放上来吗

korver · 发表于 2010-3-8 22:31:11

the residents of Town X participated in a survey to determine the number of hours per week
each resident spent watching television . the distribution of the results of the survey had
a mean of 21 hours and a standard deviation of 6 hours . the number of hours that Pat, a resident
of Town X , watched television last week was between 1 and 2 standard deviations below the
mean. which of the following could be the number of hours that Pat watched television last
week

A 30 B 20 C 18 D 12 E6

LZ问的应该是这个问题。回应楼上把原题放上来。本来也不会。求解

fanxinchao · 发表于 2010-3-8 22:37:49

是这题的……谢谢

fanxinchao · 发表于 2010-3-8 22:40:33

好像是这样做的哈……
比平均数小1-2的偏差，就是比平均数小就是6或12，就是9到15，多以选12，不知道这么理解对不对，不过答案是对的

zekerui · 发表于 2010-3-9 16:21:47

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三道数学题，有空帮我看看啊，没想明白

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