Siginificant figures calculating zprob

[Sarah Wang]

Hello everyone!

I want to calculate zprob(the area under the normal curve)
with python and I managed to find a function from the
internet.

But the problem is that the function calculates the result
with only a few significant figures. If I want to get the 
20th number of the result(z-prob) what should I do? I want
to get the confidence level of "6sigma" and all I get at the
moment is "1".

I remember that Python's long type has unlimited number of
significant figures as long as the memory allows. What about
floating point numbers?

BTW, I don't have enough knowledge in numerical analysis.

Thanks in advance,

Sarah Wang

p.s. Apologize me if I have made any mistake writing in the
posting -- I am not very goot at both English and mathematics. :)