Density function of product of random variables

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SUMMARY

The discussion focuses on deriving the density function of a new random variable Z, defined as the product of two independent random variables X and Y. The initial approach involved using convolution and logarithmic transformations, but the participants emphasized starting with the cumulative distribution function (CDF) method. Specifically, the formula P(Z ≤ z) = E_Y[P(XY ≤ z | Y = y)] is suggested as a foundational step for further development, applicable regardless of whether X and Y share the same distribution.

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  • Understanding of independent random variables
  • Knowledge of probability density functions (PDFs)
  • Familiarity with cumulative distribution functions (CDFs)
  • Basic concepts of expectation in probability theory
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khotsofalang
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suppose you have two random variables X and Y which are independent,
we want to form a new random variable Z=XY, if f(x) and f(y) are density functions
of X and Y respectively what is the density function of Z?

I tried taking logs and applying convolution, but it did not really work
 
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It isn't clear to me from your writing whether X and Y have the same distribution - you used the same name for their densities - but think about this start: it will work whether they are identically distributed or not. Start with this
[tex] P(Z \le z) = E_Y \left[P\left( XY \le z \mid Y = y\right) \right][/tex]

and see what develops.
 

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