x's expectation value in quantum physics

[Palindrom]

When I'm in a dimension higher than 1, do I need to integrate over all space (V) or only the x axis?
Thanks in advance.

[dextercioby]

When I'm in a dimension higher than 1, do I need to integrate over all space (V) or only the x axis?
Thanks in advance.

Let's consider a QM system whose states are described by the wavefunction
\psi (x,y,z) .You wish to calculate the expectation value for \hat{x} .That is nothing but the number.

<\hat{x}> =\int\int\int_{R^{3}} \psi^{*}(x,y,z) x \psi (x,y,z)

I hope your wave function is normalized/normalizable.Else,you might encounter some problems with the integration above.

Daniel.