21 Refer to the housing data in Table 9.4 The quadratic model relating selling price to size of house has fit -2.04+49.345 +6.745.

a) Interpret the coefficients of this equation. What shape does it have?

b) Find the predicted selling price for homes with (i) S=1. (ii) S-2, tiii) S = 3. Explain why the effect of a one-unit increase in 5 increases as S increases.

c) Find the S value for which this curve takes its minimum. Note that the curve increases over the entire range of possible house sizes.

d) Using size as a straight-line predictor in a bivariate model, r2 = .808, whereas R= 815 for the quadratic model. Do you think that the degree of nonlineanty is major, or minor? Do you think that the degree of linear association is strong, or weak?