f ( x ) = 1 2 π σ e − 1 2 ( x − μ σ ) 2 {\displaystyle f(x)={\frac {1}{{\sqrt {2\pi }}\sigma }}e^{-{\frac {1}{2}}\left({\frac {x-\mu }{\sigma }}\right)^{2}}}
f ( x , y ) = 1 2 π σ X σ Y e − 1 2 ( ( x − μ X σ X ) 2 + ( x − μ Y σ Y ) 2 ) {\displaystyle f(x,y)={\frac {1}{{2\pi }\sigma _{X}\sigma _{Y}}}\,e^{-{\frac {1}{2}}\left(\left({\frac {x-\mu _{X}}{\sigma _{X}}}\right)^{2}+\left({\frac {x-\mu _{Y}}{\sigma _{Y}}}\right)^{2}\right)}}
