# Expected value of bivariate pdf

Is the expected value E[x]or E[y] of a bivariate pdf fXY(xy)

\int x f(x,y)dx

or

E[y]

\int y f(x,y)dy ?

example if f(x,y) = x+y

E[X] = \int x *(x+y)dx

regards
Brendan

mathman
You need to carry out the double integral. A single integration gives the conditional expection of one variable with rexpect to the other.

So just say you had the lmits of 0<x<1 0<y<1
The expected value would be:
$E[X] = \int_{0}^{1}\int_{0}^{1} x *(x+y)dxdy = 7/12 [\latex] Is that right? Sorry, [itex] E[X] = \int_{0}^{1}\int_{0}^{1} x *(x+y)dxdy = 7/12$

regards