Radial Maze (Olton & S 1976)

[Graham Byatt]

hi,
I am currently carrying out a study looking at the effects of anterior
thalamic lesions on radial maze performance (12 arm radial maze).
I would like to transform the data as per Olton & Samuelson 1976.
The paper appears to describe the method in detail but I am still
confused about how exactly the  p(cor)expected  term is obtained. 

If anyone has had experience with this procedure I would appreciate any
help they could give.

Thanks.

Graham Byatt
Psychology Dept.
University of Canterbury
Christchurch
New Zealand

email:  g.byatt at psyc.canterbury.ac.nz