Page 178 - Microsoft Word - 00 BA3 IW Prelims STUDENT.docx

Chapter 11

Question 5

Moving averages

A time series analysis of past sales units shows the following actual and trend
figures. Calculate the seasonal variations for the data given and use the
information to predict a sales unit value for December.

Y = T + S
Actual/prediction 3 point average
Month (Y) 3 point total (T)
Jan 107
Feb 176 480 160
Mar 197 555 185
Apr 182 630 210
May 251 705 235
Jun 272 780 260
Jul 257 855 285
Aug 326 930 310
Sep 347 1005 335
Oct 332 1080 360
Nov 401
Dec

Y = T + S S = Y - T
Actual/prediction 3 point 3 point average Seasonal
Month (Y) total (T) variation (S)
Jan 107
Feb 176 480 160 16
Mar 197 555 185 12
Apr 182 630 210 -28
May 251 705 235 16
Jun 272 780 260 12
Jul 257 855 285 –28
Aug 326 930 310 16
Sep 347 1005 335 12
Oct 332 1080 360 –28
Nov 401 =360 + 25 = 385 16
Dec =410 + 12 = 422 =385 + 25 = 410 12

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