Solve a Branching Process: Xn & F(s) - Get Help Now!

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In summary: JamesonIn summary, the question asks for a proof that the expectation of a product is the same as the expectation of the individual products.
  • #1
Tranquillity
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I attach the following question about branching processes. Xn is the size of the nth generation. F(s) is the pgf of Z, the offspring distribution.

Any hints/help on how to proceed with my proof would be greatly appreciated!

Regards
 

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  • #2
Your attachment shows your attempt which is great because people don't usually help without seeing effort. Might I suggest though trying to retype your attempt in a new post using Latex? You can take a look at http://www.mathhelpboards.com/showthread.php?27-How-to-use-LaTeX-on-this-site to see how to use Latex on MHB.

Jameson
 
  • #3
The suggestion is good, though this question involves a proof and a lot of notation is involved, I would prefer to get hints and continue uploading my handwritten attempts, to show every time exactly what I think and where I have a problem.

Are you able to help me with the exact question? Thanks!

Regards
 
  • #4
Hello,

A bit late, but I can answer. Don't condition by [tex]X_1[/tex], but by [tex]X_{n-1}[/tex]. Then note that [tex]S_n=\sum_{i=1}^{X_{n-1}} Z_i^{(n)}[/tex] to write the expectation of a product : [tex]E\left[\prod_{i=1}^{X_{n-1}} s^{Z_i^{(n)}}\bigg|X_{n-1}\right][/tex] and finish it off.
 
  • #5
Hello, thanks for the reply! I have figured it out! I was asked by the exercise to condition on X1. I have finished my proof which conditions on X1. Thanks again :)
 
  • #6
Well it'd be nice if you shared it with us, for some people may need to have this kind of proof at hand :) (although I personally don't need it (Evilgrin))
 
  • #7
Moo said:
Well it'd be nice if you shared it with us, for some people may need to have this kind of proof at hand :) (although I personally don't need it (Evilgrin))

Try this :) It conditions on something similar that was so near to what I was trying to do, If you undestand what I am posting you can derive what I am asked to! Any more help I could provide that! Regards!
 

FAQ: Solve a Branching Process: Xn & F(s) - Get Help Now!

1. What is a branching process?

A branching process is a mathematical model used in probability theory to study the growth and development of a population. It involves a sequence of random variables, where each variable represents the number of offspring in the next generation.

2. How do you solve a branching process?

To solve a branching process, you need to use a generating function, denoted as F(s), which represents the probability generating function of the offspring distribution. Then, you can use the recursive formula Xn = F(Xn-1) to calculate the expected number of offspring in each generation.

3. What is the importance of solving a branching process?

Solving a branching process can help predict the long-term behavior of a population. It is used in various fields, such as biology, economics, and epidemiology, to understand the growth and spread of different species or phenomena.

4. What are some common applications of branching processes?

Branching processes have many practical applications, such as predicting the spread of infectious diseases, analyzing the growth of a company or market, and understanding the evolution of species in biology.

5. Are there any limitations to using branching processes?

While branching processes can provide useful insights, they have some limitations. They assume that the offspring distribution remains constant over generations, which may not always be the case in real-world scenarios. Additionally, they do not account for external factors that can affect population growth.

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