This is from Durrett's probability: Let X n </msub> &#x2208;<!-- ∈ --> [

prirodnogbk

prirodnogbk

Answered question

2022-07-13

This is from Durrett's probability:
Let X n [ 0 , 1 ] be adpated to F n . Let α , β > 0 with α + β = 1 and suppose
P ( X n + 1 = α + β X n F n ) = X n , P ( X n + 1 = β X n F n ) = 1 X n
Show P ( lim n X n = 0 or 1 ) = 1.
I know there is question Martingale convergence proof here but can't we prove this using levy's 0-1 law?
What can we say about levy's 0-1 law regarding Martingale Sequence?

Answer & Explanation

Oliver Shepherd

Oliver Shepherd

Beginner2022-07-14Added 24 answers

X n is a martingale, and so converges (boundedly) to a random variable X . You'll be able to write a recursion for the second moments E [ X n 2 ], leading, after a passage to the limit as n , to the conclusion that E [ X 2 ] = E [ X ].

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