Question: IQ scores are designed to have a mean of 100 and a standard deviation of 15. IQ testing is one way in which people are categorized as having different levels of mental disabilities; there are four levels of mental retardation between the IQ scores of 0 and 70.
a. People with IQ scores of 20-35 are said to have severe mental retardation and can learn only basic skills (e.g., how to talk, basic self-care). What percentage of people fall in this range?
b. People with IQ scores of 50-70 are in the topmost category of IQ scores that qualify as impairment. They are said to have mild mental retardation. They can attain as high as a sixth-grade education and are often self-sufficient. What percentage of people fall in this range?
c. A person has an IQ score of 66. What is her percentile?
d. A person falls at the 3rd percentile. What is his IQ score? Would he be classified as having a mental disability?