The data in the following table show the daily sales of pa- perback books and hardcover books at the same store. The task is to forecast the next four days' sales for paperbacks and hardcover books.
(a) Use single exponential smoothing and compute the mea- sures of forecasting accuracy over the test periods 11-30.
(b) Repeat using the method of linear exponential smoothing (Holt's method).
(c) Compare the error statistics and discuss the merits of the two forecasting methods for these data sets.
(d) Compare the forecasts for the two methods and discuss their relative merits.
(e) Study the autocorrelation functions for the forecast errors resulting from the two methods applied to the two data series. Is there any noticeable pattern left in the data?
|
Day
|
Paperbacks
|
Hardcovers
|
Day
|
Paperbacks
|
Hardcovers
|
|
1
|
199
|
139
|
16
|
243
|
240
|
|
2
|
172
|
128
|
17
|
225
|
189
|
|
3
|
111
|
172
|
18
|
167
|
222
|
|
4
|
209
|
139
|
19
|
237
|
158
|
|
5
|
161
|
191
|
20
|
202
|
178
|
|
6
|
119
|
168
|
21
|
186
|
217
|
|
7
|
195
|
170
|
22
|
176
|
261
|
|
8
|
195
|
145
|
23
|
232
|
238
|
|
9
|
131
|
184
|
24
|
195
|
240
|
|
10
|
183
|
135
|
25
|
190
|
214
|
|
11
|
143
|
218
|
26
|
182
|
200
|
|
12
|
141
|
198
|
27
|
222
|
201
|
|
13
|
168
|
230
|
28
|
217
|
283
|
|
14
|
201
|
222
|
29
|
188
|
220
|
|
15
|
155
|
206
|
30
|
247
|
259
|