fw: [問題] 兩題統計問題
※ [本文轉錄自 Grad-ProbAsk 看板]
作者: bltn (放假 找我玩啦) 看板: Grad-ProbAsk
標題: [問題] 兩題統計問題
時間: Fri Jun 9 21:15:52 2006
1.suppose that the duration of a cellular phone call is a normal random
variable with mean 2.5 minutes and variance 5 minutes. what is the
probability that a call lasts
(a)shorter than 1 minute
(b)between 2 and 4 minutes
(c)longer than 5 minutes
2.the amount of time that a student spends in the library per day is a
random variable with mean 8 minutes and standard deivation 15 minutes
Suppose that a sample of 50 students is observed . Find the probability
that the average time spending in the library per day for these student is
(a) Less than 5 minutes
(b) Between 5 and 10 minutes
(c) More than 20 minutes
懇求高手幫我解答一下囉
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