Hi everyone,

I do hope someone will be able to help me.  I have some density function of which I want to calculate some percentage points for arbitrary parameters.  I want to do this in Mathematica - with using the function "FindRoot".  It does however give me the following error:

"FindRoot::nlnum: "The function value {False} is not a list of numbers with dimensions {1} at {z} = {1.`}."

I don't even know where to start to look for a solution!  The code that I am using have been used by myself before, but only know it is giving me a problem.  Any thoughts?  Code attached in the Mathematica .nb file.

What the program is supposed to do:

There is a defined density funciton, called WGen.  It is a univariate function of z, with 5 parameters (n1, n2, r, rho, th1 and th2).

This density function's integral up to some point z is then calculated to "mimic" its distribution function (CDF).
Then, the function "h" is defined as the CDF minus the critical point - and this function is then solved for = 0 (effectively solving CDF = p).  I wish to get the value of z which will result in the CDF being equal to p.

Thanks guys, I'll really appreciate any constructive thoughts.  I'm not that well aquainted with Mathematica so I'm also still learning.