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From: "Tom Lane" <tlane@mathworks.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: fitting the norm CDF
Date: Wed, 9 Jan 2008 15:08:41 -0500
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> One more question is how I can can transform the b (fitted
> parameters) into the estimated mean and dispersion of the
> normal distribution.  From glmfit I received
> b(1) =  -3.6396 and
> b(2) =  21.6186;

Pete, the model being fit is

   p = normcdf( b(1) + b(2)*x )
      = normcdf(  (x - (-b(1)/b(2))  )/ (1/b(2))  )

so -b(1)/b(2) and 1/b(2) are I think what you are trying to get.  Try this 
after the code you have so far:

line(refx,normcdf(refx, -b(1)/b(2), 1/b(2)),'color','g')

-- Tom