If outcomes can be determined (by hidden variables or whatever), then any experiment will have a result. Thus the results cannot be determined ahead of time, so there are no hidden variables, and the results are truly random. Here’s the experiment:1) Generate a pair of entangled photons (you can do this with a down converter, which splits one photon into an entangled pair of photons). The amazing thing about entangled photons is that they always give the same result when you measure them at the same angle. This is only true for entangled photons.