Multi-Period Forecasting with Seasonality

Under seasonality, forecasts for multiple periods are given as follows  

Since the deseasonalized level forecast does not change, the forecasts for future period are only affected by their respective seasonality indices. 

Consider Example 2.3, where laptop sales by quarter for years 2008, 

and 2010 were given and we forecasted the demand for the first quarter of 2011 using exponential smoothing method with seasonality. Suppose the problem now is to forecast the sales for all the four quarters of 2011. 

In Example 2.3 (TaWe 2.3), the deseasonalized forecast for the first quarter of 2011, namely Fu was computed as 619. Thus, the actual forecasts for year 2011 are as follows  

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Multi-Period Forecasting with Seasonality and Trend... 

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