That seems a bit strange. If those 50% of the populace that are below average IQ would all use IE and everybody above 100 would use another browser, even then their average IQ would end up in the nineties. And why would anyone with a low IQ even do an online IQ-Test for fun? I don't think it's fun if you can't solve many of the puzzles. Were all applicants native speakers? A test is just as good as your grasp of the test's language, even if it has a lot of abstract parts and a user agent doesn't have that information.
The results suggested that Internet Explorer surfers had an average IQ in the low eighties