Probability first step conditioning.
Maths and statistics discussion, revision, exam and homework help.
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Re: Probability first step conditioning.
I take it this is a Markov chain of some variety? (i.e. future depends only on present state, not past states.)
Suppose you start at position 3. Then:
(a) You can go to position 1 with probability
, in which case you're absorbed to position 1 with probability 
(b) You can go to position 2 with probability
, in which case you're absorbed to position 1 with probability 
(c) You can stay at position 3 with probability
, in which case you're absorbed to position 1 with probability 
(d) You can go to position 4 with probability
, in which case you're absorbed to position 1 with probability 
Combining this information we get
Since it's a Markov chain, the reason why all the probabilities "reset" is because when you know your second position it doesn't matter where you started off.