The accompanying data on x = head circumference z score (a comparison score with peers of the same age) at 6 to 14 months of age and y = volume of cerebral grey matter (in ml) at 2 to = years of age are from a graph that appeared in the Journal of the American Medical Association (2003).

a. Construct a scatterplot for these data.
b. What is the value of the correlation coefficient?
c. Find the equation of the least squares regression line.
d. Predict the volume of cerebral grey matter for a child whose head circumference z score was 1.8.
e. Explain why it would not be a good idea to use the least squares regression line to predict the volume of grey matter for a child whose head circumference z score was 3.0.

Cerebral Grey Head Clrcumference z-Scores at 6-14 Months Matter (ml) at 2-5 yr -0.75 680 690 700 720 740 740 750 750 760 780 790 810 815 820 825 835 840 845 1.20 -0.30 0.25 0.30 1.50 1.10 2.00 1.10 1.10 2.00 2.10 2.80 2.20 0.90 2.35 2.30 2.20