X+Y | -w<=X-Y<=w



Hi,

if X and Y are Gaussian and independent and w=Inf P(X+Y |-w<=X-Y<=w) is equal to the unconditional probability P(X+Y). This implies that Z=X+Y follows a Gaussian with mean E(X)+E(Y) and Var(Z)=Var(X)+Var(Y).

If w is smaller than Inf:
Intuition suggests that Var(Z) > Var(X)+Var(Y) but does anyone know a formula / approximation for this?
And is there a approximation for the case that X and Y are dependent.

Second issue:
Can the resulting distribution of Z approximated by a Gaussian distribution?



Thank you for help.

Kind regards,
bokdan
.



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