Use the data in FERTIL3.RAW for this exercise.(i) Regress gfrt on t and t2 and save the re...

Use the data in FERTIL3.RAW for this exercise.

(i) Regress gfrt on t and t2 and save the residuals. This gives a detrended gfrt, say ,

(ii) Regress on all of the variables in equation (10.35), including t and t2. Compare the R-squared with that from (10.35). What do you conclude?

(iii) Reestimate equation (10.35) but add t3 to the equation. Is this additional term statistically significant?