Answer :
Final answer:
To determine the seasonal index for the third quarter using the regression model, substitute x = 3 into the equation ŷ = 37.9x + 57. Divide the predicted sales for the third quarter by the average sales for all quarters to find the seasonal index.
Explanation:
To determine the seasonal index for the third quarter, we can use the regression model. The regression model is represented by the equation ŷ = 37.9x + 57, where ŷ is the predicted value for sales and x represents the quarter. Since we want to find the seasonal index for the third quarter, we substitute x = 3 into the equation: ŷ = 37.9(3) + 57 = 113.7.
If we divide the predicted sales for the third quarter by the average sales for all quarters, we can find the seasonal index: 113.7 / (the average of all sales) = seasonal index. The correct answer is not provided in the options.