4

23.61

 

 

 

Σ

2

 

 

 

Cumulative error (

e ).

 

0

0.50

 

Smoothing constant (a).

 

 

 

 

 

 

 

 

2

25.11

 

Smoothing average (St-1).

 

 

 

 

 

 

 

 

3

0.42

 

Trend (Tt-1).

 

 

 

 

 

 

 

 

 

6

25.95

 

Last forecast (Dt+1).

 

 

 

 

 

 

 

The procedure is repeated for several α's.

 

 

 

 

Smoothing Constant (α)

.5 .1

.25

.2

 

 

Cumulative Error (Σe2)

23.61

25.14

17.01 18.03

 

For the selected α = .25

St+1= 24.28

 

 

 

 

 

Tt-1= 0.34

 

 

 

 

 

Dt+1= 25.64

 

 

Forecasting:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Keystrokes

Display

 

 

 

 

 

CLEAR

0.00

 

 

 

 

 

 

 

 

 

 

 

1

 

1.00

 

 

 

 

 

 

 

 

 

 

 

 

.25

0

0.75

 

 

 

 

 

 

 

 

 

 

 

 

1

0.75

 

 

 

 

 

 

 

 

 

 

 

 

24.28

2

24.28

 

 

 

 

 

 

 

 

 

 

 

.34

3

0.34

 

 

 

 

 

 

 

 

 

 

 

25.64

6

25.64

 

 

 

 

 

 

 

 

 

 

 

26

 

0.36

 

 

 

 

 

 

 

 

 

 

 

 

 

 

26.16

 

Forecast for month 9, ( t+1).

 

5

25.80

 

Expected usage for current (month

 

 

8) period, (Smoothed Dt).

 

 

 

 

0

0.25

 

α

 

 

 

 

 

 

 

 

 

 

 

2

24.71

 

Record for initial values when

 

 

 

 

3

0.36

 

month 9 actual figures become

 

 

 

available.

 

 

 

6

26.16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: At least 4 periods of current data should be entered before forecasting is attempted.

92

Page 93
Image 93
HP 12C manual Procedure is repeated for several αs