Quantum mechanics is, at least at first glance and at least in part, a mathematical machine for predicting the behaviors of microscopic particles. The effects of quantum mechanics are typically not observable on macroscopic scales, but become evident at the atomic and subatomic level.
The word "quantum" suggests that discrete changes in state occur, shifting even from one extreme to the next, rather than slowly changing in an infinitely variable process. Of interest are the Heisenberg Uncertainty Principle, and Schrödinger's Cat.
The Heisenberg Uncertainty Principle suggests we cannot tell what is, only what was. This is because the very act of observation changes reality.
Schrödinger's Cat is a paradoxical thought experiment in which a cat is imprisoned in a contrived cage. Apparatus in the cage, based on decay of atomic particles, may or may not have killed the cat. Looking in the box may, or may not kill the cat as well. The cat exists in a mixture of states, both dead and alive. At what point does the cat stop existing as a mixture of states and become one or the other?
Ergo, Observation Affects Outcomes. Well, for that matter, Observation Effects Outcomes.