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[MadMojoMonkey]

observed = measured

In this context, yes.

The act of measuring changes the initial conditions. Of course there will yield two different results based on whether or not it was observed. That's not spooky, it's totally intuitive. How do you "meausre" the velocity and location of a particle? Or, more to the point, how do you do this accurately without altering its trajectory and thus changing the conditions? Hint - you can't, see "uncertainty prinicple".

This is measurement uncertainty and it is a separate problem than quantum uncertainty laid out in the uncertainty principle.

Measurement uncertainty is a common problem. Consider measuring your car's tire's pressure. By attaching the pressure gauge to the tire, you obtain a reading by releasing some of the pressure into the tire pressure gauge. You cannot measure the pressure with that gauge without altering the pressure you're trying to measure.

This applies to quantum particles, too, but it is NOT the uncertainty principle.

The uncertainty principle says that, even with "perfect" measurement devices, you still cannot simultaneously measure the position and momentum of something to arbitrarily high precision. Those properties DON'T SIMULTANEOUSLY EXIST IN THE UNIVERSE for any particle... because particles are waves, and waves have this property.

The double slit experiment can be explained by pilot wave theory. I'm not sure what to make of it all, but the basic gist is every particle has an associated wave, and the wave essentially carves out a geomoetric path for the particle to follow. The trajectory of the particle is determined by its initial conditions, at least until we try to measure it, thus changing its trajectory.

That pilot wave is the imaginary portion to the solutions of Schroedinger's Wave Equation. Particle wave functions are complex-valued. To determine probabilities of observing certain properties of a particle, you square the wave function and integrate over some domain. The squaring eliminates all negative and complex values from the result, making them neatly measurable predictions.

There is no known way to measure a complex-valued wave, and the pilot wave theory is predicated on these imaginary solutions directing the particles' apparently random motions in deterministic ways. It's a comfortable view, but not falsifiable by any known means, so not, strictly speaking, science.