The following are quarterly totals of sales by a manufacturer of swimsuits in tens of thousands for the years 2000 to 2003:
What is a seasonal model that might be appropriate to represent such sales? Even though .the above illustrative data are inadequate, perform a seasonal analysis with the data and illustrate how to (1) estimate the Parameters of such a model, (2) use it for forecasting and (3) obtain a confidence interval for a forecast.