Is the Marginal CDF of X Correctly Defined with Two Random Variables?

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SUMMARY

The marginal cumulative distribution function (CDF) of a random variable X, given two random variables X and Y, is defined as F(x) = ∫_{-\infty}^{\infty} F(x|y)f(y)dy. The discussion clarifies that the initial expression F(x) = ∫^{F(x|y)}_{-\infty}f(y)dy is incorrect. The correct formulation requires integrating the conditional CDF F(x|y) multiplied by the probability density function (pdf) f(y). No known distribution validates the initial claim.

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zli034
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If there are X and Y two random variables. The pdf of Y is f(y), and conditional pdf of X is f(x|y). I want to find the marginal CDF of X, the F(x). Is this correct?
F(x)=\int^{F(x|y)}_{-\infty}f(y)dy

\dfrac{d}{dx}\int^{F(x|y)}_{-\infty}f(y)dy=\int^{\infty}_{-\infty}f(x|y)f(y)dy=f(x)?
 
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The density function for x is \int_{-\infty}^{\infty}f(x|y)f(y)dy.
 
Yes, I know your logic. But I found the marginal expression today. I put it here. I want to know is it correct, or under what condition I can get F(x) that way?
 
zli034 said:
Yes, I know your logic. But I found the marginal expression today. I put it here. I want to know is it correct, or under what condition I can get F(x) that way?
It is not obvious. F(x)=\int_{-\infty}^{\infty}F(x|y)f(y)dy. I don't see how you got your integral.
 
zli034 said:
Is this correct?

No. And I don't see any distribution for which it is correct.
 

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