Certain observations are probabilistic, and the correlations in them predicted by quantum mechanics cannot be reproduced by ascribing them to the traits of particles.
It means that at the lowest level, the universe is (barring faster-than-light communication, generally regarded to be false) "truly random". (No concept of an "observer" needs to be devised in order to arrive at this conclusion).
How do you know it's truly random though? Couldn't it be the result of a pseudo random process? Or universe splitting, where two universes are created, one where a coin lands head, and one where it lands tails. To the people inside, it seems random, but it's actually deterministic.
Pseudorandom means the choice is deterministically chosen by according to the state of hidden variables. Bell's theorem says there are no hidden variables that completely explain the predictions of quantum mechanics.
A many-worlds interpretation (which is consistent with QM) is basically the same as saying the result is random, because you can't predict exactly which branch any particular interaction will follow.
Certain observations are probabilistic, and the correlations in them predicted by quantum mechanics cannot be reproduced by ascribing them to the traits of particles.
It means that at the lowest level, the universe is (barring faster-than-light communication, generally regarded to be false) "truly random". (No concept of an "observer" needs to be devised in order to arrive at this conclusion).