数学prep ps110 求助~

summer0802 · 发表于 2010-11-9 17:06:10

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
(E) 6
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【答案】 D
【思路】平均數與標準差的概念
題目的數據: 平均數(mean) :21 hrs 標準差(standard deviation) : 6 hrs

由Pat 上星期看電視的時間在1~2個標準差之下可得知(between 1 and 2 standard deviations below the mean)，時間範圍應該坐落在9hrs~15hrs之間 ? 答案D 符合算出來的要求

没太懂思路的意思，那个9-15h是怎么的出来的？谢谢

summer0802 · 发表于 2010-11-9 17:14:42

求大牛现身啊啊啊啊

cicimwy · 发表于 2011-11-23 19:27:13

顶起这道题我也不会完全不明白！！！

cicimwy · 发表于 2011-11-23 19:44:10

楼主我懂了这个题的意思是这个人看电视的时间与平均数相比差了1-2个标准差的只就是21-6*2<看电视时间<21-6

数学prep ps110 求助~

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