Its also not obvious that people who went with the EU interpretation were incorrect. Language is contextual, if we were to parse the Times, Guardian, BBC, etc over the past year and see how the word "Europe" is actually used, it might be the land mass, or it might be the EU. Certainly one usage will have been more common than the other, but its not obvious to me which one it will have been.

That said, if I had noticed the ambiguity and not auto parsed it as EU, I probably would have expected the typical American to use Europe as land mass and since I think Yvain is American that's what I should have gone with.

On the other other hand, the goal of the question is to gauge numerical calibration, not to gauge language parsing. If someone thought they were answering about the EU, and picked a 90% confidence interval that did in fact include the population of the EU that gives different information about the quantity we are trying to measure then if someone thinks Europe means the continent including Russia and picks a 90% confidence interval that does not include the population of the landmass. Remember this is not a quiz in school to see if someone gets "the right answer" this is a tool that's intended to measure something.