→ a016258:X 是怎麼定的? Z<0.84 機率是0.2吧~!? 02/09 18:23
X是電瓶壽命，P(Z<0.84)=0.8吧!! = =
※ 編輯: aiaorry 來自: 220.228.251.160 (02/09 18:36)
推 ecoHYL:1.z是負值 2.兩題都是P(X<k) 02/09 19:25
→ aiaorry:感謝^^ 02/09 20:34
1.某品牌汽車電瓶壽命為平均數4年，標準差0.5年的常態分配，根據過去資料顯示有20%
的電瓶在保證期限內便失效，請問製造商之保證期多久?!
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X~N(4,0.5^2)
請問20%的機率是在右邊還是左邊呢?!
要怎麼判別呢?!
是P(X<k)=0.2 還是P(X>k)=0.2呢?!
書上寫P(X<k) = 0.2 = P( Z < 0.84 = (k-4)/0.5 )
0.84是錯的吧?!
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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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同上面的問題，
X~N(35,64)
P(X>k)=0.95 還是P(X<k)=0.95呢?
謝謝~
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