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Based on Internet IQ tests, which I know aren't really reliable, however, compared to most IQ tests administered before 15-20 years ago they're probably more reliable, My IQ has varied from 160 to 138... that's 22 points, or varying by 11, nearly 1 standard deviation (which is 15 or 16 points depending).

BTW the case of natural selection is pretty minor. And the fact that IQs have been increasing at an average rate of 3 points per decade (the Flynn effect) shows pretty clearly that something other than race and natural selection is at play with IQ test scores.

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Internet IQ tests aren't a little bit unreliable, they're very unreliable.

But beyond that, with regards to the differences you mention in score. Different IQ test types yield different scores, their only commonality RE scoring is that the 50th percentile is set to 100.

Which is why it means next to nothing when someone says 'I have a 160 IQ', unless they tell you which test they used. If you look at Mensa membership criteria for example, the admittance level is a 138 on WAIS or a 150 on Cattell B, both well respected and widely used tests - those two scores are considered the SAME score. I approximated those numbers from memory, I can't be bothered to google it while multi-tabling lol, but they're roughly right. Point is only that there is no such thing as having an IQ of x unless a test is specified, so the deviation you mention doesn't mean anything unless you had a properly administered IQ test AND it was the same IQ test type each time. It's always surprised me that this nugget of info has managed to keep itself outside of popular knowledge, considering the amount of really smart people I know that tell me 'I have an IQ of 150'.


Edit:

Dug this up from the Mensa website. These are all well respected IQ tests and the scores below represent the top 2% of the population (so eligible for Mensa). So these scores are considered the 'same':

* Cattell III B - 148
* Culture Fair - 132
* Ravens Advanced Matrices - 135
* Ravens Standard Matrices - 131
* Wechsler Scales - 132