Different Methods for Forecasting Sales

Monthly sales for National Mixer, Inc. for a seven-month period were as follows:

Month (T) - Sales (1000 UNITS)
Feb - 19
Mar - 18
Apr - 15
May - 20
Jun - 18
Jul - 22
Aug - 20

Forecast the sales volume for September using each of the following method:

a) 5-month moving average;

b) Weighted average, where the weights are - 0.60 (August), 0.30 (July), 0.10 (June)

c) Exponential smoothing with a smoothing constant equal to 0.20

d) Linear trend equation, Y = 16.86+0.5*T;