For the time series data presented in Table 9.10 calculate seasonal forecasts using the simple seasonal additive exponential smoothing model.

If we plot the time series as illustrated in Figure 9.44 we note that we have a definite pattern in the shape of the curve, which repeats over the same time period quarters.

This suggests a seasonal module would be appropriate.

Quarter 1 2 3 4 Table 9.10 1 17.15 19.87 20.53 20.78 2 16.80 15.87 17.13 18.11 3 13.85 19.67 20.29 20.94 Year 16.99 18.96 24.84 23.11 5 21.12 21.03 24.55 25.90 6 17.35 17.57 18.19 21.66