作者loveliver (糗了糗了)
看板Grad-ProbAsk
标题Re: [问题] 94北科统计
时间Thu Mar 26 00:01:12 2009
※ 引述《s911125 (江小LO)》之铭言:
: a factory produces 10 glass comtainers daily.itmay be assumed that there is a
: constant probability p=0.1 of producing a defective container.before these
: containers are stored they are inspected and defective ones are set aside.
: suppose that there is a constant probalility r=0.1 that a defective container
: is misclassified.let X equal the number of containers classified as defective
: at the end of a production day.(suppose that all containers which are
: manufactured on a particular day are also inspected on that day.) compute
: P(X=2)?
: a. 0.1937
: b. 0.1714
: c. 0.2541
: d. none of above
: 我的算法 1. 10C2*0.1^2*0.9^8=0.1937
: 2. 10C2*0.01^2*0.99^8=0.00415
: 请问哪个P是正确的 0.1 & 0.01
由机率总和定理:
则经过检测後的不良率=0.9*0+0.1*0.9=0.09
let X equal the number of containers classified as defective
at the end of a production day
X~B(10, 0.09)
则P(X=2)= C(10,2)* 0.09^2 *0.91^8 =0.1714
=>故选b.
不晓得和你手上的答案是否相同@@
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1F:推 s911125:感谢你! 原来不良率是0.09^^ 03/26 00:24