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三題統計學問題~
The spent on a cell phone is normally distributed
with mean=7 minutesand 標準差=1.8 mnutes . if you select a random sample of 20 phonecells~(a)what is the probability that the sample mean is between 6.8 and7.2 minutes?(b)what is the probability that the sample mean is between 6
5 and7 minutes?(c) if you select a random sample of 150 phone calls
what is theprobability that the sample mean is between 6.8 and 7.2 minutes?
取樣 20 個時
平均值的標準差 為 1.8 /
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