A third-order autoregressive model is fitted to an annual time series with 17 values and has the following estimated parameters and standard errors:

At the 0.05 level of significance, test the appropriateness of the fitted model.

ao = 4.50 al = 1.80 a2=0.80 = 0.24 Sal= 0.50 Sa = 0.30 Sal = 0.10