# Thread: Formula to find cumulative probability from z-score

1. ## Formula to find cumulative probability from z-score

I want a formula to calculate the cumulative normal probability from a given z-score. e.g. f(1) = 0.3413, but I can live with f(0.3413) = 1
I don't want to use a table.
I don't know or want to learn integral calculus for this, but I can use a Basic iterative program loop if required.
I used to have a calculator (radio shack EC-4004 circa 1988) that provided a formula to approximate the value as a sample program, but the manual is lost and I can't even remember the name of the mathematician credited for the formula.
Thanks for any help.

2. It sounds like you already know there is no exact formula in a closed form. There are some approximations here:

http://en.wikipedia.org/wiki/Normal_...the_normal_CDF

Wikipedia is not the most reliable source in the world so you may want to independantly verify whatever formula you choose to use.

3. I was going to show you how simple Taylor Series is here
But you don't want to see it
that's a shame