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Homework Help: Markov Chain Statistics

  1. Apr 6, 2012 #1
    1. The problem statement, all variables and given/known data
    A taxicab moves between the airport, Hotel A, and Hotel B according to a Markov chain with transition probabilities:
    P(airport → A) = 0.7,
    P(airport → B) = 0.3,
    P(A → airport) = 0.9,
    P(A → B) = 0.1,
    P(B → airport) = 0.8,
    P(B → A) = 0.2.
    A-If the taxicab starts at the airport, what is the probability that it will be at Hotel A two moves later?
    B-Suppose the taxicab starts at the airport with probability 0.6 and starts at Hotel A and Hotel B with probability 0.2 each. What is the probability that it will be at Hotel B two moves later?
    C- In the long run, what fraction of visits will the taxicab make to each of the three locations?

    2. Relevant equations

    3. The attempt at a solution
    I have gotten the answer for parts A & C but I don't understand at all how I would set up the matrix with part B. My initial though was that the matrix was

    0 .2 .8
    .2 0 .8
    .6 .4 0

    with the first row/column being hotel A, the second row/column being hotel B, and the third row/column being the airport

    then by squaring the matrix I got
    .52 .32 .16
    .48 .36 .16
    .08 .12 .8

    and then to get B I added up .32 + .12=.44 which was wrong. What did I do wrong?
  2. jcsd
  3. Apr 7, 2012 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    For (b): in two moves, P{at B} = P{at B|start at port}*P{start at port} + P{at B|start at A}*P{start at A} + P{at B|start at B}*P{start at B}. The conditional probabilities are given by P*P.

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