quality:corruption, information:filtering
For complex variables

If x {\displaystyle x} is a scalar complex -valued random variable, with values in C, {\displaystyle \mathbb {C},} then its variance is E, {\displaystyle \operatorname {E} \left,} where x ∗ {\displaystyle x^{*}} is the complex conjugate of x. {\displaystyle x.} This variance is a real scalar.