作者aiaorry (我不想皱眉头)
看板Grad-ProbAsk
标题[商管] [统计]-高应用95-观光所
时间Tue Feb 9 18:18:27 2010
1.某品牌汽车电瓶寿命为平均数4年，标准差0.5年的常态分配，根据过去资料显示有20%
的电瓶在保证期限内便失效，请问制造商之保证期多久?!
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X~N(4,0.5^2)
请问20%的机率是在右边还是左边呢?!
要怎麽判别呢?!
是P(X<k)=0.2 还是P(X>k)=0.2呢?!
书上写P(X<k) = 0.2 = P( Z <
0.84 = (k-4)/0.5 )
0.84是错的吧?!
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2.A bakery shop sells loayes of freshly made French bread.
Any unsold loaves at the end of the day are either discarded or sold
elsewhere at a loss. The demand for this bread has followed a normal
distribution a mean of 35 loves and a standard deviation of 8 loaves.
How many loaves should the bakery make each day so that they can meet the
demand for this product 95% of the time?
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同上面的问题，
X~N(35,64)
P(X>k)=0.95 还是P(X<k)=0.95呢?
谢谢~
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◆ From: 220.228.251.160
1F：→ a016258:X 是怎麽定的? Z<0.84 机率是0.2吧~!? 02/09 18:23
X是电瓶寿命，P(Z<0.84)=0.8吧!! = =
※ 编辑: aiaorry 来自: 220.228.251.160 (02/09 18:36)
2F：推 ecoHYL:1.z是负值 2.两题都是P(X<k) 02/09 19:25
3F：→ aiaorry:感谢^^ 02/09 20:34