作者dick0631 (立志打败邪恶的ETS军团)
看板Statistics
标题Re: [问题]统计三个问题
时间Sat Jan 5 02:34:26 2008
※ 引述《oceanboy0605 ()》之铭言：
: 以下我有统计三题我各位帮忙，除了有过程之外，
: 最好需要有详细解说我会比较容易了解～谢谢
: 1.求算二项分配的众数
先查一下什麽叫众数。
然後再试P(X=x)=P(X=x+1) ,X~Bin(n,p)
: 2.If 5% of the tires purchased by a cab company last less than 6 months
: and if 20 tires are purchased, calculate the probability that at most
: 2 of the tires will expire in six months using.
这一题有很难吗？
X_i~bin(1,P(tires 6个月内 expire)=0.05)
Y=X_1+...+X_20~bin(20,P=0.05)
: If the mean length of life a tire 2 years. Use the exponential distribution
: to calculate the probability that the life of a tire will be less than
: 6 months?
W~指数分配 mean length of life a tire 2 years
计算 P(W<6)=1-P(W>6)
: 3.Suppose the lifelime of an electronic tube has an exponential distribution
: with a mean time of 1/λ hours. Find the expected lifelime of a tube,given
: that the tube has lasted at least T hours.
前二题都很懂，再来研究这题吧！
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1F：推 sasoman:第一题应该P(X=x)>=P(X=x+1)、P(X=x)>=P(X=x-1)才对吧 01/05 08:52
2F：推 youngsam:楼上正解 01/05 14:12