Hi,Brother,
If you want to know the exact answer you have to use computer.Twft is right,it is from generating function.
007's answer is reasonable.I do it by subnormal distribution.Mean=5.5*7=38.5.Sigma=(38.5-7)/4=7.875,z1=19.5/7.875=-2.476,z2=(20.5-38.6)/7.875=-2.286.P(E)=T(2.476)-T(2.286)=.9933-.9888=.0045.
回複:依次任取7個小於等於10的正整數,求其和為20的概率?
所有跟帖:
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I'll give the answer in the next couple days.
-皆兄弟也-
♂
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06/07/2010 postreply
18:45:32
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0.0026355 is the exact answer,if I do well.
-jinjing-
♀
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06/08/2010 postreply
14:36:55
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maybe, you are right. My answer is 0.0026544, but not confident
-皆兄弟也-
♂
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06/09/2010 postreply
00:20:27