... ERF([lower limit,]upper_limit) . With a single argument ERF returns the error function, defined as erf(x) = 2/sqrt(pi)* integral from 0 to x of exp(-t*t) dt. If two arguments are supplied, they are the lower and upper limits of the integral. If either @lower_limit or @upper_limit is not numeric a #VALUE! error is returned. This function is upward-compatible with that in Excel. ... ERF(0.4) equals 0.428392355. ERF(1.6448536269515/SQRT(2)) equals 0.90. ... ERFC . ...