The standard transformation formula of normal distribution is f (x) = φ [(x-μ)/σ]. Standard normal distribution is a very important probability distribution in the fields of mathematics, physics and engineering, which has great influence in many aspects of statistics.

The expected value μ=0, that is, the normal distribution under the condition that the symmetry axis of the curve image is Y axis and the standard deviation σ= 1 is recorded as n (0, 1). The probability density function curve of normal distribution is bell-shaped, so people often call it bell-shaped curve. What we usually call standard normal distribution is a normal distribution with the mean value of position parameters of 0 and the standard deviation of scale parameters of 1.