The following quarterly time series gives the number of units sold during 5 years at a boat dealership.
(a) Find the four-quarter centered moving averages.
(b) Plot the series and the moving averages on a graph.
(c) Compute the seasonal-irregular component.
(d) Compute the seasonal indexes for all four quarters.
(e) Compute the deseasonalized time series for sales.
(f) Fit a linear trend equation to the deseasonalized sales.
(g) Forecast the number of units sold in each quarter of Year 6 (using seasonal and trend components).