[R] Freeman-Tukey arcsine transformation

[Sebastian P. Luque]

On Tue, 13 Mar 2007 14:15:16 -0400,
"Bos, Roger" <roger.bos at us.rothschild.com> wrote:

> I'm curious what this transformation does, but I am not curious enough
> to pay $14 to find out.  Someone once told me that the arcsine was a
> good way to transform data and make it more 'normal'.  I am wondering if
> this is an improved method.  Anyone know of a free reference?

My Zar¹, says this is just:


p' = 1/2 * (asin(sqrt(x / (n + 1))) + asin(sqrt((x + 1) / (n + 1))))


so solving for x should give the back-transformation.  It is recommended
when the proportions that need to be "disciplined" are very close to the
ends of the range (0, 1; 0, 100).


+---- *Footnotes* ----+
¹ @BOOK{149,
  title = {Biostatistical analysis},
  publisher = {Prentice-Hall, Inc.},
  year = {1996},
  author = {Zar, J. H.},
  address = {Upper Saddle River, New Jersey},
  key = {149},
}


-- 
Seb