Approximations to the Normal Distribution Function and An Extended Table for the Mean Range of the Normal Variables

Abstract

This article presents a formula and a series for approx¬imating the normal distribution function. Over the whole range of the normal variable z, the proposed formula has the greatest absolute error less than 6.5e - 09, and series has a very high accuracy. We examine the accuracy of our proposed formula and series for various values of z’s. In the sense of accuracy, our formula and series are su¬perior to other formulae and series available in the literature. Based on the proposed formula an extended table for the mean range of the normal variables is established