Chapter 13 Forecasting
2. Dalworth Company
a. Three-month simple moving average
Month Actual Sales Three-Month Simple Absolute Absolute Squared
(Thousands) Moving Average Error % Error Error
Forecast
Jan. 20
Feb. 24
Mar. 27
Apr. 31 (20+24+27)/3 = 23.67 7.33 23.65 53.73
May 37 (24+27+31)/3 = 27.33 9.67 26.14 93.51
June 47 (27+31+37)/3 = 31.67 15.33 32.62 235.01
July 53 (31+37+47)/3 = 38.33 14.67 27.68 215.21
Aug. 62 (37+47+53)/3 = 45.67 16.33 26.34 266.67
Sept. 54 (47+53+62)/3 = 54.00 0.00 0.00 0.00
Oct. 36 (53+62+54)/3 = 56.33 20.33 56.47 413.31
Nov. 32 (62+54+36)/3 = 50.67 18.67 58.34 348.57
Dec. 29 (54+36+32)/3 = 40.67 11.67 40.24 136.19
Total 114.00 291.48 1,762.20
Average 12.67 32.39 195.80
Such results also can be obtained from the Time Series Forecasting Solver:
b. Four-month simple moving average
Month Actual Sales Four-Month Simple Absolute Absolute Squared
(Thousands) Moving Average Error % Error Error
Forecast
Apr. 31
May 37 (20+24+27+31)/4 = 25.5 11.50 31.08 132.25
June 47 (24+27+31+37)/4 = 29.75 17.25 36.70 297.56
July 53 (27+31+37+47)/4 = 35.5 17.50 33.02 306.25
Aug. 62 (31+37+47+53)/4 = 42.00 20.00 32.26 400.00
Sept. 54 (37+47+53+62)/4 = 49.75 4.25 7.87 18.06
Oct. 36 (47+53+62+54)/4 = 54.00 18.00 50.00 324.00
Nov. 32 (53+62+54+36)/4 = 51.25 19.25 60.16 370.56
Dec. 29 (62+54+36+32)/4 = 46.00 17.00 58.62 289.00
Total 124.75 309.71 2,137.68
Average 15.59 38.71 267.21
Similarly, using Time Series Forecasting Solver, we get:
c.*e. Comparison of per ...