IQ Tests

I don't understand the purpose of IQ tests. There are so many different ways of thinking so how can you measure intelligence and turn it into a number? And what good would it serve to take one?

Still, I'd always wondered how I'd do. But what if I got a low score? I mean, I know taking these kinds of tests don't amount to anything and besides, they only test one particular way of thinking, but what if it told me that I'm way below average? So I'd always been too scared to take one. Until last week. I don't know what I was thinking. I guess I wasn't thinking at all. I came across an on-line IQ test and found myself taking it.

http://iqtest.com
I know that IQ tests differ and results vary depending on what kinds of questions are on it, but I did pretty well on this one. I scored 140 which supposedly is within the top 2% of the population (just a few points short of Genius level). Go me!!!

I mentioned this score to a friend and she felt like taking it, too, but the one I took was meant for native English speakers, so she got on-line and found one that doesn't rely on language ability whatsoever.
http://www.unnmei.com/iq.html
What a surprise when she scored on the lower end of average intelligence -- 90. I consider her pretty smart, so this score proves that these kinds of tests can't possibly be accurate. I tried this one, too, and scored the exact same as before -- 140.

http://www.allthetests.com/tests/iq-test.php3
On this one I scored 141, which supposedly is "Brilliant".

I got lucky in having taken three tests that happened to test a way of thinking that I would score well on. I don't plan on taking any more. What if the next one scores low?