Newark College would like to include seasonality in its GPA forecasting model. The average GPA of the

Question:

Newark College would like to include seasonality in its GPA forecasting model. The average GPA of the study body for each year was broken down into the average GPA by semester (Fall, Spring, Summer) and can be found in the Excel file grade inflation by semester. xlsx.
a. Using multiplicative decomposition, forecast the average GPA for the student body for each semester during 2014.
b. Interpret the meaning of the seasonal components.
c. Calculate the MAD for this forecast.