JJ 和 Prep 中标准方差题求牛人指点！

legationq

1. 有11個數95,96,97,98,99,100,101,102,103,104,105,106, 標準差greater than three and less than four, 問數列中與中數median within one deviation的有多少個

選A six, 有98,99,100,102,103,104共6個

中數101, 以上數字都在一個標準差內. 比如說101-98=3<deviation. 其他的照推.

現在看來101也可以, 應該選7個吧. 答案可能有錯, 大家再討論

这题我不明白 题中说有11个数,可是作者给了12个数.那中数就为100.5了.

那么是不是该选8个      97,98,99,100,101,102,103,104,    明天考了请指证啊.

110.
    

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

(A) 30

(A) 30

(A) 30

(B) 20

(C) 18

(D) 12

(E) 6

答案选D

答案选D

这题不太理解题的意思.好心人教教吧.

[此贴子已经被作者于2008-11-30 17:40:58编辑过]

legationq

顶

hafeifei

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?

1-2个deviations ,所以这个区间在9，15，21，27，33。

题目说below the mean，只有D符合题目问题的要求。

[此贴子已经被作者于2008-11-30 22:06:12编辑过]