HP 12c Solutions Handbook page 157

•
1
c = exp -- -
n
•
----------------------------------------- -
a = exp
• Where S , S
1
•
•
•
• a, b and c are determined by solving the three equations above simulta-
neously.
Forecasting With Exponential Smoothing
• a = smoothing constant (0 < a < 1)
• X = actual current period usage
t
2
 
S S – S
1 3 2
----------------------------------- -
 
S + S 2S
–
 
1 3 2
b 1 S S
– –
2 1
2
n
b b – 1
, and S are:
2 3
n
∑
S = Iny
1
i = 1
2n
∑
S = Iny
2
i = n + 1
= n c ln + b ln a
i
n + 1
= n c ln + b ln
i
156
1
  T
-- -
1 t = S t +
 
+ 1
n
b – 1
-------------- -
b 1 –
n
b – 1
-------------- -
a
b 1 –
t