In studying the effects of heredity and environment on intelligence, scientists have learned much by analyzing the IQ scores of identical twins who were separated soon after birth. Identical twins have identical genes, which they inherited from the same fertilized egg. By studying identical twins raised apart, we can eliminate the variable of heredity and better isolate the effects of environment. Following are the IQ scores of identical twins (first-born twins are x) raised apart.

Use the rank correlation coefficient to test the claim of no correlation between the two variables. Use a significance level of α = 0.05.

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xi 107 96 103 90 96 113 86 99 109 105 96 89 y 97 116 107 99 85 108 102 105 100 93 Based on data from "IQ's of Identical Twins Reared Apart," by Arthur Jensen, Behavioral Genetics.