How are the change of variables formula from calculus and the change of variables formula for expectation related?

139 Views Asked by At

How is the change of variables formula from multivariable calculus $$\int_{\Omega} f \circ \phi \cdot |\text{Jac}(\phi)| = \int_{\phi(\Omega)} f$$ related to the change of variables formula for expectations? $$E(g(X)) = \int g(x)f(x)\ dx.$$ Can you use the first to derive the second? Is the link between them made clear using measure theory? If $X$ is a continuous random variable on the probability space $(\Omega, \mathcal{F}, P)$, I know that its expectation is given by $$E(X) = \int_{\Omega} X\ dP.$$ But I'm not sure where to go from here.