Using the data in Problem 5-33, develop a multiple regression model to predict sales (both trend and seasonal components), using dummy variables to incorporate the seasonal factor into the model.
In Problem 5-33, A major source of revenue in Texas is a state sales tax on certain types of goods and services. Data are compiled and the state comptroller uses them to project future revenues for the state budget. One particular category of goods is classified as Retail Trade. Four years of quarterly data (in $ millions) for one particular area of southeast Texas follow:

Use this model to predict sales for each quarter of the next year. Comment on the accuracy of thismodel.

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QUARTER YEARI YEAR 2 YEAR3 YEAR 4 225 254 255 299 218 247 243 292 234 265 264 327 250 283 289 356