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Math Help - Probability Plotting

  1. #1
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    Jul 2011
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    Probability Plotting

    I know i am being very stupid atm, but i really can seem to get the right ans off my calc. Its just part b that i need help with please ...


    Q5 The ranking points for n = 10 chess players were: 3.2, 3.9, -5.6, 6.5,
    -13.8, 4.7, 12.9, 15.3, -10.6, -6.6. The logistic distribution has cumulative distribution function
    F (y) = ey
    1 + ey −∞ < y < ∞.

    It is thought chess ranking points follow a logistic distribution and it is
    proposed to test this assumption using probability plotting.
    (a) Rank the observations into numerical order such that x1 < x2 <
    ... < xn.
    (b) Find yi such that F (yi) = i
    n+1
    for i = 1, ..., n.

    I have the answer yi = log ( i
    n + 1 − i )
    I thought this was right but when i go to sub in the values i cant get the right ans. I was using i=1...10, eg where i=1, yi= -13.8.
    so i would e -13.8 then rearrange to get n on its own! but its wrong

    Pretty please help me, thanks
    
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  2. #2
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    Joined
    Jul 2011
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    Re: Probability Plotting

    hmm sorry the format seems to have messed up there. please see attached picture for the question
    2bb6a.jpg at Free Image Hosting
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