New car sales for a dealer in Cook County, Illinois, for the past year are shown in the following table, along with monthly indexes (seasonal relatives), which are supplied to the dealer by the regional distributor.
|
Month
|
Units Sold
|
Index
|
|
Jan.
|
640
|
.80
|
|
Feb.
|
648
|
.80
|
|
Mar.
|
630
|
.70
|
|
Apr.
|
761
|
.94
|
|
May
|
735
|
.89
|
|
Jun.
|
850
|
1.00
|
|
Jul.
|
765
|
.90
|
|
Aug.
|
805
|
1.15
|
|
Sept.
|
840
|
1.20
|
|
Oct.
|
828
|
1.20
|
|
Nov.
|
840
|
1.25
|
|
Dec.
|
800
|
1.25
|
Plot the data. Does there seem to be a trend?
Deseasonlize car sales.
Plot the deseasonlized data on the same graph as the original data. Comment on the two graphs.
Assuming no proactive approach on the part of management, discuss (no calculations necessary) how you would forecast sales for the first three months of the next year.
What action might management consider based on your findings in part b?