The question of probability is of great importance above all because it could be a basis for deciding between determinism and indeterminism ("determinism or indeterminism). If the probability of quantum mechanics can only be interpreted indeterministically, as many physicists believe, determinism is refuted. 

What is probability

General
Determinate probability
Indeterminate probability

Two ways to interpret quantum mechanics

The fact that for individual quantum objects basically no more than the probability of their location can be calculated (cf. indeterminate probability above) is undisputed ("Heisenberg's uncertainty principle"). However, there are various ways of interpreting this fact. 

Indeterministic interpretations
Deterministic interpretations

Deterministic interpretations explain the impossibility of calculating more than the probable location of a single quantum object, for example, by the fact that quantum mechanics is not complete. While indeterministic interpretations assume that no further causes exist, Bohmian mechanics, for example, assumes that there are parameters or causes that are fundamentally hidden. They exist, but they cannot be determined in principle. This trick in turn explains the behaviour of the individual "quantum objects" as epistemically probable and is thus deterministic. 

However, since these hidden parameters or variables cannot be detected in principle, it can only be a speculation that can neither be proven nor disproven. Excitingly, however, Bohmian mechanics can be calculated and it leads to the identical results as, for example, the most widespread interpretation of quantum mechanics, the "Copenhagen interpretation.

Whether Bohmian mechanics is the "true Jacob" is not up for discussion here. However, the fact that deterministic interpretations are possible should be enough, after the explanations of indeterministic interpretations, to finally put the focus more on those.

Conclusion

Indeterministic interpretations of quantum mechanics that assert indeterministic probability are only conceivable if contradictions can exist in reality (which makes it precisely inconceivable), if probability can be inexplicably based on absolute chance and if they can explain the interaction between indeterministic elements and deterministic elements also required by such interpretations. Since deterministic interpretations cannot be ruled out so far (Scarani: possibility of determinism), they are fundamentally preferable to indeterministic interpretations, since indeterministic probability cannot be formulated without contradictions.