Sum of non-independent rv's

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In summary, the sum of non-independent random variables (rv's) is a mathematical concept used in probability theory to describe the sum of two or more random variables that are not independent. It differs from the sum of independent rv's by not having a simple formula and requiring more advanced techniques to calculate. Examples of non-independent rv's include the heights of siblings, grades of students in a group project, and stock prices of companies in the same industry. They can be used in real-world applications in various fields and are analyzed and calculated using techniques such as conditional probability, joint distributions, and covariance. These techniques help determine the relationship between the variables and their combined behavior.
  • #1
joserse46
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f(x,y) = (1/x) for 0≤y≤x≤1

A new rv Z=X+Y where X,Y not independent find the pdf of z

My approach

F(z) = P(Z≤z) = ∫∫fXY(x,y) dx dy x= -∞ to ∞ y= 0 to z-y

f(z) = d/dz(F(z)) = ∫fXY(z-y,y) dy y= -∞ to ∞ (using Leibnitz)

where i am stuck is this doesn't converge
 
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  • #2
(this thread belongs in the homework forums)

f(x,y) might not be a valid pdf
 

1. What is the "sum of non-independent rv's"?

The sum of non-independent random variables (rv's) is a mathematical concept used in probability theory to describe the sum of two or more random variables that are not independent.

2. How is the sum of non-independent rv's different from the sum of independent rv's?

The sum of independent rv's follows a well-known mathematical formula, while the sum of non-independent rv's does not have a simple formula and requires more advanced techniques to calculate.

3. What are some examples of non-independent rv's?

Some examples of non-independent rv's include the heights of siblings, the grades of students in a group project, and the stock prices of companies in the same industry.

4. Can non-independent rv's be used in real-world applications?

Yes, non-independent rv's are commonly used in various fields such as finance, engineering, and biology to model complex systems and make predictions.

5. How are non-independent rv's analyzed and calculated?

The analysis and calculation of non-independent rv's involve techniques such as conditional probability, joint distributions, and covariance. These techniques help to determine the relationship between the variables and their combined behavior.

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