Standard normal distribution
The simplest case of a normal distribution is known as the standard normal distribution. This is a special case where μ=0 and σ=1, and it is described by this probability density function:
phi(x) = frac{e^{- frac{scriptscriptstyle 1}{scriptscriptstyle 2} x^2}}{sqrt{2pi}},
The factor scriptstyle 1/sqrt{2pi} in this expression ensures that the total area under the curve ϕ(x) is equal to one.[6] The
1
/
2
in the exponent ensures that the distribution has unit variance (and therefore also unit standard deviation). This function is symmetric around x=0, where it attains its maximum value 1/sqrt{2pi}; and has inflection points at +1 and −1.