You are examining the errors of a monthly one-step-ahead forecasting model that you have been using for eight years. You have 96 months of forecasts, realizations, and errors. You plot the errors and calculate the correlogram for these errors and find the following: Does the output below suggest that the forecasts have been optimal forecasts?
LAG AC PAC Q.Stat Prob
1 .580 .580 102.79 0
2 .030 -.461 103.06 0
3 -.316 -.141 133.85 0
4 -.368 -.056 175.66 0