(a) Using the data in Problem 7.1 (page 253), estimate a multiple regression model of the birth rate explained by GNP, the growth rate and the income ratio. Comment upon:

(i) the sizes and signs of the coefficients,

(ii) the significance of the coefficients,

(iii) the overall significance of the regression.

(b) How would you simplify the model?

(c) Test for the joint significance of the coefficients on growth and the income ratio.

(d) Repeat the above steps for all 26 observations. Comment.

(e) Do you feel your understanding of the birth rate is improved after estimating the multiple regression equation?

(f) What other possible explanatory variables do you think it might be worth investigating?