[philonossis]

"Three samples of a substance were subjected to analysis with each sample analyzed by a different different technique.  The results were:

Technique I: 34.1% of Q and 65.9% of X
Technique II: 34.12% of Q and 65.88% of X
Technique III: 34.12497% of Q and 65.87503% of X

Is the substance that was analyzed likely an element, a compound, or a mixture?"

My answer was mixture.

Is this correct or is there no way to tell?

[Wald_ron]

Does each test show a fixed ratio of atoms?

[MOTOBALL]

By inspection, each technique used gives a successively greater (claimed) accuracy;

II and III give the same % value for  Q and X to 2 decimal places

I and II  give the same % value for Q and X to 1 decimal place.

I would say that each technique gives the same value for Q and X---this is possible, but not LIKELY,  if the substance is a mixture of Q and X.

I believe you have a compound, UNLESS the techniques are measuring isotopic ratios in an element.

Can you find an element that has the specified composition ??

[philonossis]

I had said mixture, but the book said compound.

I now think I thought that the last figure could not be rounded to be the same as the first two.  That would have meant a variable composition, which defines a mixture.

But I think my rounding was incorrect, and all figures can be rounded to the same three figures.

The problem was about how to tell a mixture, compound, and element. We had not reached atoms.

[Borek]

All three round down to the same result. That means data you have doesn't allow to say they are different.