作者speedoyi (我可以)
看板Statistics
标题[问题]机率和统计问题
时间Fri Dec 28 20:43:35 2007
1.
题目：X1,X2,X3 br three independent random times for three
subprojects. If these subprojects are in series, we are interested in
the sum Y1=X1+X2+X3. If these are in parallel, then interested in
Z=max(X1,X2,X3), each of these random variables has U(0,1)
find pdf of Y ?
以下是我的做法
因为X1 X2 X3独立 所以f(x1,x2,x3)=1
令Y1= X1+X2+X3
Y2= X2+X3
Y3= X3 然後作变数变换 得到f(y1,y2,y3)=1 , 0<y3<y2<y1<1
=> y1 y2
f(y1)= ∫0 ∫0 1 dy3dy2 = (1/2)(y1^2) 0<y1<1
总觉得我这样做还少了些什麽
因为我只算出 0<y1<1 可是看过去似乎 0<y1<3
也就是说 我是不是还要算2<y1<3 这范围的pdf呢 如果是 又该从何下手
谢谢各位大大指教~~
2. x 0 1 2 3 4 5
Frequency 6 10 14 13 6 1
let the table represent a summary of a sample of size 50 from a
binomial distribution having n=5 Find the mle of P(X>=3)
谢谢各位指教~~
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※ 编辑: speedoyi 来自: 218.170.113.182 (12/28 20:44)
※ 编辑: speedoyi 来自: 218.170.113.182 (12/28 20:45)