The manager of the Petroco Service Station wants to forecast the demand for unleaded gasoline next month so that the proper number of gallons can be ordered from the distributor. The owner has accumulated the following data on demand for unleaded gasoline from sales during the past 12 months:
Month Gasoline Demanded (gal.)
October 800
November 725
December 630
January 500
February 645
March 690
April 730
May 810
June 1,200
July 980
August 1,000
September 850
a. Compute a 2-month moving average demand forecast for the months of December to September. Calculate MAD, MAPD and MSE.
b. Compute a 2-month weighted moving average demand forecast for the months of December to September. Calculate MAD, MAPD and MSE. (w1=0.6, w2=0.4)
c. Assume the demand forecast for November is equal to the actual demand of October, 800. Compute an exponentially smoothed demand forecast for the months of November to September, using an α value of .30. Calculate MAD, MAPD and MSE.
d. Assume the demand forecast for October is also 800. Compute an adjusted exponentially smoothed demand forecast for the months of November to September. Calculate MAD, MAPD and MSE. (with α = .30 and β=.20).
e. Compute linear trend line demand forecast for the months of October to September. Calculate MAD, MAPD and MSE.
f. Compare the five forecasts by using MAD, MAPD and MSE and indicate which seems to be more accurate.