Consider the following sample regressions for the linear, the quadratic, and the cubic models along with their respective r2 and adjusted r2.

linear quadratic cubic
intercept 9.66 10.00 10.06
x 2.66 2.75 1.83
x2 na −0.31 −0.33
x3 na na 0.26
r2 0.810 0.836 0.896
adjusted r2 0.809 0.833 0.895

pictureclick here for the excel data file

a.
predict y for x = 1 and 2 with each of the estimated models. (round intermediate calculations to 4 decimal places and final answers to 2 decimal places.)

linear
y-hat quadratic
y-hat cubic
y-hat
x = 1

x = 2

b. select the most appropriate model.

quadratic model
linear model
cubic model