RE: HP48-HP50G : Error functions ERF(z), FRESNEL integrals, PROBIT, etc.

[Gil]

Last version 16.09
at last post (page 3)with comments or here

Wikipedia:
"In statistics, for non-negative values of x, the error function has the following interpretation: for a random variable Y that is normally distributed with mean 0 and standard deviation 1/√2, erf x is the probability that Y falls in the range [−x, x]."

Therefore, with mean 0, variance (1/√2)² = 1/2 = 0.5 and UTPN command, the following short steps enable to easily and accurately calculate
Erf(x) = « 0 .5 ROT UTPN -2 * 1 +»
and Erfc(x) = « 1 SWAP ERF -» or « 0 0.5 ROT UTPN 2 * ».

For complex argument, see below.
For inverse Erf & Erf, see also below.