Probability Density Function of |X|^(1/2)+|Y|^(1/2)+|Z|^(1/2) with N(0,1)

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Discussion Overview

The discussion revolves around determining the probability density function (pdf) of the expression |X|^(1/2) + |Y|^(1/2) + |Z|^(1/2), where X, Y, and Z are independent random variables following a normal distribution with mean 0 and variance 1 (N(0,1)). The scope includes theoretical exploration and mathematical reasoning related to probability distributions.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant requests assistance in finding the pdf of the given expression involving independent normal variables.
  • Another participant suggests starting with the distribution of |X|^(1/2) and notes that the other distributions will be identical, implying a method for finding the distribution of their sum.
  • A participant confirms the independence of the variables but inquires about standard procedures for deriving the pdf, especially when dealing with more than three random variables.
  • Another response proposes using a normal (Gaussian) pdf for the random variables but presents an incorrect formulation, leading to a correction from another participant.
  • A participant outlines a potential approach, suggesting that the distribution of |X| is a standard result and that a transformation can be applied to find the distribution of |X|^(1/2), noting that the same applies to |Y| and |Z| due to their identical distribution.

Areas of Agreement / Disagreement

Participants generally agree on the independence of the variables and the need to find the distribution of |X|^(1/2). However, there is disagreement regarding the methods to derive the pdf, with some participants providing differing approaches and corrections to earlier claims.

Contextual Notes

Some assumptions regarding the distributions and transformations may be missing, and the discussion does not resolve the specific steps needed to obtain the final pdf. The complexity of handling more than three random variables remains unaddressed.

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Could anyone help me figure out the the probability density function (pdf) of |X|^(1/2)+|Y|^(1/2)+|Z|^(1/2) if X, Y and Z are distributed normally with mean 0 and variance 1, N(0,1) ?

Thanks in advance.
 
Last edited:
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Are your variables independent? If so, first work out the distribution of [tex]|X|^{1/2}[/tex]. The other distributions will be identical and you can use standard procedures to find the distribution of their sum.
 
Yes, the variables are independent. But what are the standard procedures? It there a easier way to get the pdf if one has more random variables than three?
 
Last edited:
If X, Y, and Z, are distributed normally, just make them a normal (gausian) PDF of a random variable.

X=Ae^(ax). You're lucky that you can use little x,y, and z for your random variables to match up with their distributions.
 
"X=Ae^(ax). " That isn't the form of a normal distribution.

Okay, suppose [tex]X \sim n(0,1)[/tex]. Think this way.

1) You should be able to write down the distribution of [tex]|X|[/tex] - it's a pretty
standard result, and if you're working on this problem I'm guessing you know this.
2) Use a standard transformation (if [tex]W = |X|, find the distribution of square root of W). This gives the distribution of [tex]|X|^{1/2}[/tex].<br /> 3) Since [tex]X, Y[/tex] and [tex]Z[/tex] are i.i.d, the same is true for <br /> <br /> [tex] |X|^{1/2} + |Y|^{1/2} + |Z|^{1/2}[/tex]<br /> <br /> so the distribution of their sum should be relatively easy to obtain.[/tex]
 

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