Umm...well, the phrasing is quite stupid. I took it once as an American, once as a Non, both times got 16 (also, got the same question wrong both times). They considered 16 a good score though...
It's a stupid quiz though. Questions are worded quite ambiguously. It proves nothing. The statistics are hardly evidence...I mean, if it even tracks the results, I took the test as an American, and I am not. I'm sure others have done the same. They fail miserably with this quiz, and look like dubmasses doing it.