The seasonal indexes and actual quarterly turnover (in R millions) for 2008, 2009 and 2010 in the hotel industry in Cape Town are as follows:
|
Season
|
Seasonal index
|
2008
|
2009
|
2010
|
|
Summer
|
136
|
568
|
604
|
662
|
|
Autumn
|
112
|
495
|
544
|
605
|
|
Winter
|
62
|
252
|
270
|
310
|
|
Spring
|
90
|
315
|
510
|
535
|
(a) De-seasonalise the hotel industry turnover data for 2008 to 2010.
(b) Plot both the original and the de-seasonalised quarterly turnover data for the Cape Town hotel industry from 2008 to 2010 on the same axis.
(c) Calculate a trendline equation for the quarterly turnover.
(d) Estimate the seasonally adjusted turnover in the Cape Town hotel industry for the summer and autumn seasons in 2011.
(e) Repeat (b) above using the Insert > Chart > Line option in Excel.
(f) Re-compute the trendline equation in (c) using Excel's Add Trendline option.