is described by the DSM (diagnostic and statistical manual) as: a disorder characterized by intellectual function that is significantly below average: specifically that of an individual with a measured IQ of 70 or below on tests with a standard deviation (the variance) of 15.

MENTAL RETARDATION (MR): "Individuals with an IQ measured less than 70, but with a standard deviation of no more than 15 are normally diagnosed with mental retardation."
Cite this page: N., Pam M.S., "MENTAL RETARDATION (MR)," in, April 7, 2013, (accessed July 13, 2020).