11.9. Recent UN data from several nations on y = crude birth rate (number of births per 1000 population size), X| = women's economic activity (female labor force as percentage of male), and X2 = GNP

(per capita, in thousands of dollars) has prediction equation y = 34.53 — 0.13xi — 0.64x2.

(a) Interpret the coefficient ofx\.

(b) Sketch on a single graph the relationship between y and X] when X2 = 0, X2 = 10, and X2 = 20. Interpret the results.

(c) The bivariate prediction equation with x\ is y = 37.65 - 0.31xi. The correlations are ryxx = -0.58,ryX2 = -0.72, and = 0.58.

Explain why the coefficient ofxj in the bivariate equation is quite different from in the multiple predictor equation.