The following are the first 30 residuals obtained when a tentative model was fitted to a time series:

???? Residuals 1--6 0.78 0.91 0.45 −0.78 −1.90 −2.10 7--12 −0.54 −1.05 0.68 −3.77 −1.40 −1.77 13--18 1.18 0.02 1.29 −1.30 −6.20 −1.89 19--24 0.95 1.49 1.08 0.80 2.02 1.25 25--30 0.52 2.31 1.64 0.78 1.99 1.36 Plot the values and state any reservations you have concerning the adequacy of the model.