IQ

IQ is a statistical measure, meant primarily for use in research, or for determining learning rate, either directly or indirectly by comparison over time.

IQ tests themselves are not unbiased, and correlate extremely well to absurd tasks such as reciting numbers backwards, and moderately well to tasks such as determining matching line lengths.

They are, in the proper (clinical or research) hands, extremely useful instruments for the analysis of intelligence, and useful instruments for establishing a baseline in psychological science.