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Can anyone help me out with the following question?

Q. What is the probability of the event that randomly selected composition of $n$ has a second part and that second part is $1$?

I know that the expected number, $E(X)$ that the first part of a randomly selected composition of $n$ is $2- 1/2^{n-1}$.

This problem is from 'A walk through Combinatorics' by Bona. Thanks,

  • 0
    What is the random variable $X$? Is it the number of parts in the composition?2012-04-09
  • 0
    I think that you have a typo in the third paragraph. Is $E(X)$ supposed to be the expected value *of* the first part of a randomly selected composition of $n$?2012-04-09

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