Random Walk Question: Expected Value, Variance & Lim n→∞

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SUMMARY

The discussion focuses on the expected value and variance of a random walk defined by independent and identically distributed (iid) increments. It establishes that for a random walk Sn = X1 + X2 + ... + Xn, the expected value is E(Sn) = nµ and the variance is Var(Sn) = n∂². The conclusion drawn is that lim n→∞ Sn = +∞ if the mean µ is greater than zero, and lim n→∞ Sn = -∞ if µ is less than zero, confirming the behavior of the random walk as n approaches infinity.

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Homework Statement



Let (X1, X2, ..., Xn,...) be iid increments (with mean µ and variance ∂^2) of a random walk Sn=X1+X2+...+Xn. What are the expected value, variance of Sn?
Prove that lim n-> ∞ Sn =+ ∞ if µ>0 and lim n-> ∞ Sn =- ∞ if µ<0

Homework Equations





The Attempt at a Solution


I found that E(Sn)=nµ and Var(Sn)=n∂^2. I am not sure how to do the second part though.
 
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What is the definition of lim Sn?
 

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