I think you're talking about electron spin, which is how quantum mechanics is typically tested in reality (since marbles, as macroscopic objects, can't be in superposition). You'd entangle two electrons and one would have a spin of 1/2 and one would have a spin of -1/2, but until one is observed they'd be in a superposition of both. When one is measured, the other "decides" on a spin (the opposite spin).