The mathematical notation for the statistical average of some quantity is Dirac's bra-ket notation ($\langle Q\rangle$).

This allows us to summarize the results of the experiments as follows: if we begin with $A$ along some axis $\hat{m}$ and prepare a spin of $\sigma = +1$, then orient $A$ along $\hat{n}$, and take measurement, the statistical value is $\langle \sigma \rangle = \hat{n} \times \hat{m}$.

Effectively, quantum systems behave non-deterministically, with statistically random results, but repetition of experiments, provides results that match classical physics, up to a point.