A project (courtesy of Howard Garber) is constructed to prevent the decline of intellectual performance in children who have a high risk of the most common type of mental retardation, called cultural-familial. It is believed that this can be accomplished by a comprehensive family intervention program. Seventeen children in the high-risk category are chosen in early childhood and given special schooling until the age of 4 1/2. Another 17 children in the same high-risk category form the control group. Measurements of the psycholinguistic quotient (PLQ) are recorded for the control and the experimental groups at the age of 41 years.
Do the data at the bottom of the page strongly indicate improved PLQs for the children who received special schooling? Use the Wilcoxon rank-sum test with a large sample approximation: Use a = .05.