Question: This problem uses an SPSS data set called HW5_1.sav. Market research was conducted for a national retail company to compare the relationship between sales and advertising during the warm Spring and Summer seasons as compared with the cool Fall and Winter seasons. See page 256 for the data table (note that Warm season = 0 and Cool season = 1).

a. Identify a single regression model that uses the data for both warm and cool seasons and that defines straight-line models relating sales revenue (Y) to advertising expenditure (X) for each season. Fit this single regression model using SPSS and report the prediction equation (Y regressed on X) for each season (warm and cool).

b. Test whether straight lines for cool and warm seasons coincide (use ?=0.05).

c. Test H₀: “The lines are parallel” vs. H_A: “The lines are not parallel” (use ?=0.05).

d. In light of your findings in b and c, interpret your findings (feel free to provide a plot of the two fitted straight lines if you feel that it will aid your interpretation).