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Statistics question (poisson distribution, multivariate )

  1. Oct 2, 2011 #1
    1. The problem statement, all variables and given/known data

    On average, 2.5 telephone calls per minute are received at a corporation's switchboard. Making appropriate assumptions about the distribution ( provide justification ), find the probability that at any given minute there will be more than 2 calls.

    2. Relevant equations

    No idea.

    3. The attempt at a solution

    No idea.



    1. The problem statement, all variables and given/known data
    Let the joint p.d.f of X and Y, f(x,y), be given by

    ..................x
    ............1.....2.....3
    y..1.....0.3..0.2..0.1
    ....2 ....0.1..0.1..0.2
    (ignore the dots)
    a) Determine marginal densities
    b) compute the means and variances of X and Y
    c) Calculate sigma(?) xy = cov (X,Y) and the correlation coefficient ρ. Are X and Y independent ?
    d) Let Z = X+Y. determine k(z)+P(Z=z), z = 2,3,4,5. determine the mean and variance.

    2. Relevant equations

    good question

    3. The attempt at a solution

    I don't have one




    Well, how do I do this? I do not understand it. If anybody has some insight on either problem, I'd appreciate it.
     
    Last edited: Oct 2, 2011
  2. jcsd
  3. Oct 2, 2011 #2
    Got the first one now. About the 2nd one - I THINK I now have b and partly c. but c required the marginal densities, correct ( for the correlation coefficient ) ? I don't know how to do that. The example in the book just tells me ok here it is..without explaining how to get it.
     
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