There's no such thing as a person's IQ. It varies. Change the IQ test and you change the IQ. Change the examiner, the day of the test, the person's mood, or the examiner's alertness, and you change the IQ. Test the person 12 times and you might get a dozen different IQs.

-- Alan S. Kaufman

from "IQ Testing 101 (Psych 101)"