一條有關nCr既題目

2010-11-04 7:23 am
it is known that10%of the appliances producted by a production plant are defective.
Five of those aplliances are going through QC inspection.
What is the probability that 4 out of the 5 appliances are defective?

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回答 (2)

2010-11-04 8:29 am
✔ 最佳答案
P(4 out of the 5 appliances are defective)= P(4 appliances are defective and 1 appliance is normal)4 out of the 5 have 5C4 ways , = (5C4) (10%)^4 (1 - 10%)^1= 5 * 0.01% * 90%= 0.045%



2010-11-07 15:05:33 補充:
這是二項分佈吧 。

正常機會 = 0.9
次品機會 = 0.1

排好第 1 2 3 4 5 件 , 例子 :

0.1 * 0.1 * 0.1 * 0.1 * 0.9 代表 1 2 3 4 壞 , 5 正常之機會

0.1 * 0.1 * 0.9 * 0.1 * 0.1 代表 1 壞 2 壞 , 3 正常 , 4 壞 5 壞之機會

這些不同的好壞次序有 5C4 種, 每種機會都是 (0.9) (0.1)^4

所以是 (5C4) (0.9) (0.1)^4
2010-11-07 7:31 pm
哩...介唔介意解釋下,睇完唔係好明條式點解係咁定
唔該你


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