At this point it is worth remembering some basic facts about the meaning of correlation. This equality suggests a possible problem with r, which is a commonly used measure of strength of association. By relying on r rather than R2, the impact of X on Y can be made to seem much greater than it is. These are not impressive results. The MRI study by Andreasen et.
Body size correlates very strongly with brain size.
Head circumference is an imperfect measure of brain size, but it is the most widely used craniometric statistic, employed by pediatricians to evaluate brain growth in children. Stature is but one of several ways of assessing body size. In table two I have divided head circumference by stature to show fractional units of head circumference per unit of stature. To facilitate comparison I have transformed these values into Z scores using the arithmetic mean of the means. Notice that sample 10, Black enlisted Air Force Women, has a Z score of 2.44, that is over 2 SD above the mean.