(Continuation of Problem XXXXXXXXXXa) For the oldest child, find the regression of FEV1 on (i) weight and age; (ii) height and age; (iii) height, weight, and age. Compare the three regression...

(Continuation of Problem 8.13.) a) For the oldest child, find the regression of FEV1 on (i) weight and age; (ii) height and age; (iii) height, weight, and age. Compare the three regression equations. In each regression, which coefficients are significantly different from zero? b) Find the correlation matrix for the four variables. Which pair of variables is most highly correlated? least correlated? Heuristically, how might this explain the results of part (a)?

PROBLEM 8.13

For the lung function data described in Appendix A, find the regression of FEV1 on weight and height for the fathers. Divide each of the two explanatory variables into two intervals: greater than, and less than or equal to the respective median. Is there an interaction between the two explanatory variables?