I typically ask people to take this one because I like it. One person asked if it’s accurate.
Here’s what I can say: it’s normed by a vocab test. The GSS 10-word vocab test (called WORDSUM) correlates with IQ at 0.71, which is pretty darn good. This is to say that Mensa could just give a ten-word vocab test (with words chosen with graduated difficulty) and admit anyone who aces it, and be correct in doing so most of the time.
[Ed: More precisely…a little more than half of the time. That’s assuming I’m remembering correctly, and 128 is still the Mensa entry requirement.]
A perfect wordsum indicates an IQ of roughly 128, as I calculated…here.
So that’s really all I can say. There is a systemic bias in terms of internet users who take IQ tests, but it is mostly accounted for by this norming effort. A person could speculate that people on the internet who take online IQ tests tend to have disproportionately higher verbal IQ and lower spatial IQ, in which case the “norm” would be too high, and your score would be too high.
But I think the plus-minus 6 points covers this pretty well.
It’s also important to note that IQs (and IQ related effects) are more accurate and more important in aggregate- when talking about demographics rather than individuals.