Who writes IQ tests? They must be insanely smart if they can write a test to measure everyone else's intelligence AND know the answers, amirite?

It's usually many, many people who contributed.

IE, one group of people who may be experts on one part of the human brain/thought process wrote one section, another group who are very knowledgable in another field of intelligence wrote another, etc.

In case anyone is wondering:
One of the first people who was at the very foundation of the IQ-test as we nowadays know it, was Alfred Binet.
Of course, many other people before and after him contributed to it too, though mainly to research on what intelligence actually is. Here's an overview:
http://www.indiana.edu/~intell/periodIndex.shtml

Intelligence is not, knowing what the answers are to factual questions, but the extent of your ability of solving problems or getting things to the right conclusion, compared to others. ( <- This is my interpretation after all and people are bound to disagree with it. )
So, based on this, I don't know if I can YYA or NO this post...

I write them