[問題] 我想請問一題有關機率的問題
Let us choose at random a point from the interval (0,1) and let the
random variable X1 be equal to the number which corresponds to that point.
Then choose a point at random from the interval (0,x1), where x1 is the
experimental value of X1. and let the random variable X2 be equal to the
number which corresponds to this point.
(a)Make assumptions about the marginal pdf f(x1) and the conditional
pdf f(X2│x1)
(b)Compute P(X1+X2>=1)
第一小題課本後面給的答案是
f(X2│x1)=1/x2 , 0<x2<x1<1
但我不了解的是為什麼機率值不等於一，而且我對f(x1)是多少也沒什麼概念
第二小題課本後面給的答案是
P(X1+X2>=1)= 1 - ln2
請各位高手指點我一下，謝謝你們
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