What is the standard deviation typically used in IQ testing?

The standard deviation commonly used in IQ testing is 15. This choice is based on the design of many standardized intelligence tests, including the Wechsler Adult Intelligence Scale and the Stanford-Binet Intelligence Scales, which were calibrated so that a score of 100 represents the average IQ, with scores distributed according to a normal curve.

With a standard deviation of 15, approximately 68% of the population scores within one standard deviation of the mean (between 85 and 115), and about 95% scores within two standard deviations (between 70 and 130). This allows for a clear understanding of how individuals' IQs compare to the average within the general population.

The other options, while they may correspond to different measures or smaller scales of variability, are not the standard used in widely recognized IQ tests. Thus, 15 remains the accepted standard deviation for assessing intelligence through these tests.