The simplest case of a normal distribution is known as the standard normal distribution
which is described by this probability density function:
${\displaystyle \varphi (x)={\frac {1}{\sqrt {2\pi }}}e^{-{\frac {1}{2}}x^{2}}}$
this is for one random variable.
how about 2 random variables, namely, is there a similar concept for joint probability, something like standard normal joint probability distribution?
I've searched this on math.stackexchange.com and got '0 results'.
any clue?
This is called The Standard Bivariate Normal Distribution
a pair of independent random variables X and Y, each follows the standard normal distribution ${\displaystyle X \sim \ {\mathcal {N}}(0,1)}$, and ${\displaystyle Y \sim \ {\mathcal {N}}(0,1)}$
For a constant $\rho$ with $-1< \rho <1$, define random variables
and then
more info is here.