The NORMSDIST function returns the result of the standard normal
cumulative distribution function for a particular value of the random
variable X. The Excel function adheres to the following
mathematical approximation, P(x), of the following standard normal cumulative distribution function (CDF)
P(x) = 1 -Z(x)*(b1*t+b2*t^2+b3t^3+b4t^4+b5t^5)+error(x), where
Z(x) = (1/(sqrt(2*pi()))*exp(-x^2/2))
t = 1/(1+px)
p = 0.2316419
b1 = 0.319381530
b2 = -0.356563782
b3 = 1.781477937
b4 = -1.821255978
b5 = 1.330274429
with the following parameters:
abs(error(x))<7.5 * 10^-8
The NORMSDIST function returns the result of the standard normal
CDF for a standard normal random variable Z with a mean of 0 (zero) and a standard deviation of 1. The CDF is found by taking the integral of the following standard normal probability density function
Z(x) = (1/(sqrt(2*pi()))*exp(-x^2/2))
from negative infinity to the value (z) of the random variable in question. The result of the integral gives the probability that Z will occur between the values of negative infinity and z.