I took two different IQ tests on same day, as offered by Mensa. CTMM and a British test whose name I forget. I did 20 or 25 points worse on the CTMM than I did on the other test. To me, it seemed like the writers of the CTMM were on drugs. I did better on the British test even though I'm an American. So it's important not to take the tests all that seriously.
Mensa turned out to be boring. My guess is that people who had better things to do were doing them.
P.S. The article above could use a bit of editing. Mostly for grammar.