作者yitsung (夜冲弟)
看板Grad-ProbAsk
标题Re: [商管] [统计] 机率
时间Fri Jan 29 21:14:00 2010
※ 引述《Nocp (冲浪..被浪冲 傻傻分不清)》之铭言：
: Many products can operate if out of n parts , k of them are
: working . Say n=20 and k =17 .Say p=0.05 is the probability that
: a part fails .Assuming independence ,what is the probability that
: the product operates ?
: 请问...这是考什麽?! 感觉像是考串并联
: 可是又解不出来... ...
应该是说一个产品有20个零件，只要17个以上的零件没坏的话这个产品就能用
令X代表20个零件里没坏的数目，则 X ~ Bin(20，0.95)
20 17 3 20 18 2
能用的机率即 P( X >= 17 ) = ( )(0.95) (0.05) + ( )(0.95) (0.05)
17 18
20 19 20 20
+ ( )(0.95) (0.05) + ( )(0.95)
19 20
= 0.9841
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 58.114.139.188