For Exercises 13.46 to 13.49, see pages 693–694; for 13.50, see page 699; and for 13.51 and 13.52, see pages 705–706.

Question 13.50

13.50 Seasonality ratios for Amazon sales data.

CASE 13.1 In Example 13.18 (pages 675–676), the seasonal component was estimated with the use of indicator variables. As an alternative, the seasonality can be captured with seasonal ratios computed by means of moving averages.

  1. Use the moving-average approach to compute seasonal ratios and report their values.
  2. Produce and plot the seasonally adjusted series. What are your impressions of this plot?
  3. Fit and report an exponential trend model fitted to the seasonally adjusted series.
  4. Provide a forecast for Amazon sales for the future period of . How does this forecast compare with the forecasts provided in Example 13.18?

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