What Is the Official IQ Scale?

There are many different interpretations of IQ, but the original scale says that above 140 points indicates genius or near-genius intelligence, 120 to 140 implies very superior intelligence, 110 to 119 is superior intelligence and average intelligence lies at 90 to 109 points. On the low end, 80 to 89 points indicates low average intelligence, 70 to 79 points implies borderline deficiency and 69 points and below indicates extremely low intelligence.

IQ scores are subjective to each test and typically are based on a number of sample scores with the median being set at 100 and statistical tools such as a bell curve distribution to calculate the score of each individual. In general, average intelligence lies between 85 and 115 IQ points, which is one standard deviation plus or minus 100 and contains 50 percent of test-takers according to normal distribution.

Psychologists may use any of seven different IQ tests, each of which uses different methods to determine the intelligence of an individual, but places scores in similarly distributed rankings. As a result, an individual may score differently between tests by as much as 10 points. In addition, an individual is likely to receive a different score on the same IQ test each time he takes it.