Thread: 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


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