From Wiki:
Quote:
|
An intelligence quotient, or IQ, is a score derived from one of several different standardized tests designed to assess intelligence. When modern IQ tests are constructed, the mean (average) score within an age group is set to 100 and the standard deviation to 15.[1] Today almost all IQ tests adhere to the assignment of 15 IQ points to each standard deviation, but this has not been the case historically. Approximately 95% of the population have scores within two standard deviations of the mean. If one SD is 15 points, then 95% of the population would be expected to have an IQ within a range of 70 to 130.
|
I interpret this to mean that the measurement is guaranteed to change over time. Years, by definition, but perhaps over shorter periods as well.