Operations Management - Forecasting



Operations Management - Forecasting

Time

Sales

Moving averages

Centered moving average

Seasonal Irregular Value

Seasonal Index

Seasonally Adjusted Sales

1

16

16

2

21

15.750

15.875

1.323

1.281

16.395

3

9

15.500

15.625

0.576

0.623

14.443

4

18

15.750

15.625

1.152

1.108

16.249

5

15

15.750

15.750

0.952

0.918

16.336

6

20

16.250

16.000

1.250

1.281

15.613

7

10

17.250

16.750

0.597

0.623

16.051

8

18

18.000

17.625

1.021

1.108

16.245

9

17

19.000

18.500

0.919

0.918

18.519

10

24

19.000

19.000

1.263

1.281

18.735

11

13

19.250

19.125

0.680

0.623

20.867

12

22

18.750

19.000

1.158

1.108

19.856

13

17

18.500

18.625

0.913

0.918

18.519

14

25

18.750

18.625

1.342

1.281

19.516

15

11

19.000

18.875

0.583

0.623

17.657

16

21

19.750

19.375

1.084

1.108

18.953

17

18

20.750

20.250

0.889

0.918

19.608

18

26

21.667

21.208

1.226

1.281

20.297

19

14

19.500

20.583

0.680

0.623

22.472

20

25

25.000

22.250

1.124

1.108

22.563

Seasonally adjusted sales figure as a percentage of the predicted value

Time

Predicted Sales (PS)

Seasonally Adjusted Sales (SAS)

SAS/PS*100

1

2

15.528

16.395

105.583

3

15.882

14.443

90.939

4

16.236

16.249

100.080

5

16.59

16.336

98.468

6

16.944

15.613

92.144

7

17.298

16.051

92.791

8

17.652

16.245

92.029

9

18.006

18.519

102.849

10

18.36

18.735

102.042

11

18.714

20.867

111.504

12

19.068

19.856

104.132

13

19.422

18.519

95.350

14

19.776

19.516

98.685

15

20.13

17.657

87.714

16

20.484

18.953

92.525

17

20.838

19.608

94.097

18

21.192

20.297

95.776

19

21.546

22.472

104.297

20

21.9

22.563

103.027

The linear predicted trend line shows significant trend values because the cyclical variation shows that there is a very minor difference that could not be sustained because in the second part of the time, the seasonally adjusted sales were $16.395 million and the predicted trend value for the same time period was $15.528 million.

The percentage change determines that the seasonally adjusted sales were only 5% more than the predicted which ...