Question: Identical twins, separated at birth and reared apart, provide researchers with a natural “controlled” experiment in which the interplay between heredity and environment can be examined. One researcher suggests that differences in education may influence differences in I .Q. scores. In particular, the researcher believes that twins with a higher level of education tend to have higher verbal I.Q. scores. The table below shows the verbal I.Q. scores for four pairs of identical twins reared apart, where one member of the pair (twin A) completed a higher level of education than the other member (twin B):

Is there evidence that the mean verbal I.Q. score of twin members with a higher level of education is larger than the mean verbal I.Q. score of their siblings? Test using α = .01. Compute the effect size.