The file S12_56.xlsx contains monthly time series data for total U.S. retail sales of building materials (which includes retail sales of building materials, hardware and garden supply stores, and mobile home dealers).
a. Is seasonality present in these data? If so, characterize the seasonality pattern and then de-seasonalize this time series using the ratio-to-moving-average method.
b. If you decided to de-seasonalize this time series in part a, forecast the de-seasonalized data for each month of the next year using the moving average method with an appropriate span.
c. Does Holt’s exponential smoothing method, with optimal smoothing constants, outperform the moving average method employed in part b? Demonstrate why or why not.