Depends on the test. E.g. some IQ tests measure the size of your vocabulary. IIRC, the reason why this works is that people with a higher IQ tend be to quicker at learning the meaning of a word from its context, and therefore accumulate a larger vocabulary. That makes the size of your vocabulary adequate as a rough proxy for IQ—but only within your age group, since people older than you have had more time to accumulate a large vocabulary.
That’s true for children, but as intelligence solidifies at ~16-20 it doesn’t make sense to include age after that.
Depends on the test. E.g. some IQ tests measure the size of your vocabulary. IIRC, the reason why this works is that people with a higher IQ tend be to quicker at learning the meaning of a word from its context, and therefore accumulate a larger vocabulary. That makes the size of your vocabulary adequate as a rough proxy for IQ—but only within your age group, since people older than you have had more time to accumulate a large vocabulary.