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Forecasting Multiplicative decomposition
4 seasons
Input Data Seasonal Index Computation Forecast Error analysis
Period
Actual
value (Y)
Time
period (X)
Centered
average
Seasonal
ratio
Seasonal
index
Unseason
alized
value
Unseason
alized
Forecast
Seasonali
zed
Forecast
Error
Absolute
error
Squared
error
Absolute
% error
Quarter 1 42.9 1 0.800 53.597 53.180 42.566 0.334 0.334 0.112 0.78%
Quarter 2 48.5 2 0.890 54.519 54.043 48.077 0.423 0.423 0.179 0.87%
Quarter 3 54.1 3 55.013 0.983 0.977 55.379 54.907 53.638 0.462 0.462 0.213 0.85%
Quarter 4 74.1 4 55.350 1.339 1.336 55.472 55.770 74.498 -0.398 0.398 0.159 0.54%
Seasonal Ratios
Season 1 Season 2 Season 3 Season 4
0.811 0.888 0.961 1.332
0.808 0.901
Average 0.800 0.890 0.977 1.336
Forecasts for future periods
Period
Unseason
alized
forecast
Seasonal
index
Seasonali
zed
forecast
17.000 66.996 0.800 53.624
20.000 69.586 1.336 92.954
Problem 11-40
40.0
50.0
60.0
75.0
90.0
Actual vs. Forecast
