作者rock1985 (疾風)
看板Math
標題[機統] 機率統計問題
時間Sat Apr 23 12:54:46 2011
The monthly revenue for a Wal-Mart store is normally distributed with the
average equal to $8.2 million and the standard deviation equal to $1.3 million
1)What is the probability that a randomly selected Wal-Mart store has
monthly revenue exceeding $10 million.
2)What is the threshold value that defines the highest 10 percent of monthly
revenue at a Wal-Mart store.
3)A sample of 34 Wal-Mart store is randomly selected, what is the probability
that the average monthly revenue of the sample exceeds $8 million.
題目是我朋友的mid-term 雖然我學過一點機率統計
但是實在不知道要怎麼解題
只知道可能會用到Z-chart之類的來解題
所以想請問大家一下要怎麼解題
可以稍微幫我朋友 順便幫我複習一下
感謝大家
第2題的部分
我想到的是從平均值去加一個某個大小的標準差
去計算10%的位置在哪裡
不過還是不太確定，所以麻煩大家教我一下
Thank you
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◆ From: 96.246.248.5
1F：推 vicwk :Q(1.281552) = 0.1 04/23 13:21
2F：→ yhliu :X～N(8.2,1.3^2), P[X>10]=1-Φ((10-8.2)/1.3) 04/23 13:51
3F：→ yhliu :3) Xbar～N(8.2,1.3^2/34) 04/23 13:52
4F：→ yhliu :P[Xbar>8] = 1-Φ((8-8.2)/(1.3/√34)) 04/23 13:53