※ 引述《Nocp (衝浪..被浪沖 傻傻分不清)》之銘言：
: 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 ?
: 請問...這是考什麼?! 感覺像是考串並聯
: 可是又解不出來... ...
應該是說一個產品有20個零件，只要17個以上的零件沒壞的話這個產品就能用
令X代表20個零件裡沒壞的數目，則 X ~ Bin(20，0.95)
20 17 3 20 18 2
能用的機率即 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
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