The way I saw it, we lived in a deterministic universe. And all the claimed randomness in the quantum world was just hidden factors about the nature of reality that we didn't know. Then I heard about Bell's inequality and how it takes out the possibility of hidden factors. So i saw this video on Bell's inequality From what I gather, the hidden factors the person in this video talks about aren't the hidden factors I thought about when asking myself this question. The hidden factors I thought of were our lack of knowledge about the true nature of these quantum objects. Also, I think it makes sense to say that if the seemingly random quantum world makes up the every day deterministic world (like me dropping a ball and it falling) that we see, then the quantum world should have hidden properties that we don't know exist which make it seem as if it is random. And if time were to be reversed (And every single factor is reversed along with time) and these experiments re-done, then they would have the exact same outcome. So is it impossible for these hidden factors to exist? Do our experiments prove that randomness exists or do they show only that randomness could exist and we don't know because of these hidden factors?