Question March 2006

Discussion in 'CT3' started by Neetu Verma, Apr 4, 2008.

  1. Neetu Verma

    Neetu Verma Member

    1)-Question 6 in paper March 2006
    Explain the solution ,I am not understand properly the equation of x & y.

    2)Question 8 ,Part(i) in same paper,
    Why, we take X=(>=)3
     
    Last edited by a moderator: Apr 8, 2008
  2. I found this one difficult when I did the paper.

    Try and think about how you would standardize the X rv
    x -- n(u, s^2)

    (x-u)/sqrt(s^2) -- N(0,1)

    This is so you can use the Z values in the tables as they are N(0,1)

    ie P(X<x) = P(Z< (x-u)/sqrt(s^2) )
    u = mu
    s^2= sigma sqaured
    sqrt is square root

    normally you look for (x-u)/sqrt(s^2) in the tables, well now we have simulated this by looking up the values in the table from the U(0,1) random numbers. Examiners have given us a "slight" HINT: Notice how the values correspond nicely to values in the tables.

    We are equating z = (x-u)/sqrt(s^2)

    Rearrange x = z*sqrt(s^2) + u
    so from the answer line 1 is x = 200 +10(0.180) = 201.80

    Take this value and use in Y|X=x -- N(x,1)
    P(Y<y) = P(Z < (y-x)/1)
    Equate
    z = y - x
    Rearrange
    y = z + x
    y = 0.930 + 201.80

    and so on.

    Imagine a the discrete disbn of x - poi(u)

    if we sum over all possible x x=0, 1, 2, ....
    we get a total of 1

    i.e. P(0) + P(1) + P(2) + P(3) + P(4) + P(5)....... = 1

    we require P(0) + P(1) + P(2) + P(everything else) = 1

    P(everything else) = P(X>=3) = 1 - P(X<= 2)

    Hope I have helped. :)
     
  3. Neetu Verma

    Neetu Verma Member

    Thanks for the help,
    Actually ,I want to know why we consider '>3' value ,According to the question ,TO determine the probability of only 0,1,2,or 3 ,but not mention >3.
    So why we consider >3
     
  4. Michael

    Michael Member

    The question states "However, the policy is limited such that only the first three claims in any one year are paid."

    If we let C be the number of potential claims, and N be the number of claims that are paid, then:

    C ~ Poi(0.8)

    P(N = 0) = P(C = 0)
    P(N = 1) = P(C = 1)
    P(N = 2) = P(C = 2)
    P(N = 3) = P(C >= 3)
    as a maximum of 3 claims will get paid, regardless of how many more potential claims there are.
     

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