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Unformatted text preview: probabilities p, 1p , in other words S n = X 1 + + X n and the { X i } are i.i.d. random variables with distribution P ( X i = 1) = p and P ( X i =1) = 1p. Fix a positive integer b > 0, and let T be the rst hitting time of the point b : T ( ) = inf { n 1 : S n ( ) = b } . If the walk never hits b , in other words the set { n : S n ( ) = b } is empty, then T ( ) = . Calculate the expectation ET . Be sure to justify everything....
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 Spring '09
 Reed
 Probability

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