Many tests in school, military and private - let's just say it would be near one of the ends of a bell curve.
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Imagine someone born with the brainpower of Einstein, but NO education at all....primative location. Now imagine your avg degree holder. I am confident that I could tell which is which in 2 mins of conversation(assuming we all spoke a common language) and a written test would not be fair.
Amazing mental powers can be present in someone that can't tie a shoe.........savants - are they genius? I've only ever heard of one person that had savant "talents" and was still basically "normal."
It is always a big debate on what intelligence really is.....so how to measure it depends.