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