Return to the quadratic regression specification of equation (13.19). The predicted value of yi from this specification is

(a) Change xi by Δx. Demonstrate that the new predicted value is

(b) Subtract the expression for ˆyi from the result of part a to obtain

(c) State the assumption that is necessary in order to approximate the relationship in part b with

(d) Starting with the answer to part

c, prove that

Transcribed Image Text:

= a+bx+bx.