[NOTES/QM-06005] Probability and Average Value

Starting with the postulates of quantum mechanics, it shown that the average value of a dynamca variable is given by\begin{equation}
 \langle A \rangle_\psi  =
\frac{\langle\psi|\hat{A}|\psi\rangle}{\langle{\psi}|{\psi}\rangle}
\end{equation}