From the U.K. private sector housing starts (X) for the period 1948 to 1984, Terence Mills obtained the following regression results* :
a. On the basis of these results, is the housing starts time series stationary or no stationary? Alternatively, is there a unit root in this time series? How do you know?
b. If you were to use the usual t test, is the observed t value statistically significant? On this basis, would you have concluded that this time series is stationary?
c. Now consider the following regression results: