Your task is to estimate the ice cream sales for a certain chain in New England. The company makes available to you quarterly ice cream sales (Y) and informs you that the price per gallon has approximately remained constant over the sample period. You gather information on average daily temperatures (X) during these quarters and regress Y on X, adding seasonal binary variables for spring, summer, and fall. These variables are constructed as follows: DSpring takes on a value of 1 during the spring and is zero otherwise, DSummer takes on a value of 1 during the summer, etc. Specify three regression functions where the following conditions hold: the relationship between Y and X is (i) forced to be the same for each quarter; (ii) allowed to have different intercepts each season; (iii) allowed to have varying slopes and intercepts each season. How would you test which model fits the data the best
