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STATS325/721 - Test 2021
发布时间:2022-09-04
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STATS325/721 - Test 2021
1. A discrete time Markov chain with state space I = {A,B,C,D,E,F} is represented by the following transition diagram:
1 3
A
1 2
3 4
(a) Find the communicating classes. For each class, state its period and whether it is recurrent or transient. [2]
(b) Find the probability of hitting state E before B given X starts in A. [4]
(c) Find the expected time to irst hit state B starting from state F . [4]
2. A Markov chain X = (Xn )nN0 with state space I = {1, 2, 3} is represented by the
transition diagram 1
3
1
2
(a) Write down the one-step transition matrix P for X .
(b) What general properties should an equilibrium distribution T satisfy? [2]
(c) Calculate equilibrium distribution T for X . [2]
(d) After a very long period of time, what is the probability that X will be found
(e) What is the long term proportion of time spent in state 3? [1]
(f) Calculate the long term average value of X, that is, limn→8 1n 对
Xn . [2]
3. The discrete time Markov chain X = (Xn )n0 with state space I = {A,B} and one-step transition matrix P given by
)
(a) Find the equilibrium distribution T of X . [2]
(b) Find the eigenvalues of P . [2]
(c) Find U1 , U2 , and λ 1 ,λ2 ∈ R such that Pn = λ1(n)U1 + λ2(n)U2 , for n ≥ 0. [3]
(d) Find an expression for P(X2 = B;X5 = B|X0 = A). [2]
(e) Is X time reversible? Justify your answer. [1]