Performance on Training and Holdout Data. Two different models were fit to the same time series. The first 100 time periods were used for the training set, and the last 12 periods were treated as a holdout set. Assume that both models make sense practically and fit the data pretty well. Below are the RMSE values for each of the models:

a. Which model appears more useful for explaining the different components of this time series? Why?

b. Which model appears to be more useful for forecasting purposes? Why?

Training set Holdout set Model A 543 Model B 669 690 675