An IQ test is a measure of a particular sort of intelligence - problem solving. Its results are used throughout the world as they are fairly accurate. This guy from Nigeria explains it very well.

https://www.quora.com/Is-it-true-that-the-blacks-in-Sub-Saharan-Africa-have-the-lowest-IQ

The real issue here is that you don't want to believe that an IQ test actually measures intelligence. There is no such thing as having an ability to do a test, but not being able to do the real thing. That is why schools and corporations measure IQ - because there is a direct correlation.

There's a very simple reason why some people can't do tests - they don't know the answers. If they knew the answers, the test would be easy.

We're now done with this conversation.