The management of an office complex in central Johannesburg wants to understand the pattern of energy consumption (i.e. energy costs related to heating and air- conditioning) in the complex. They have assembled quarterly data on energy costs for the past three years (in R100 000s).
|
Year
|
Quarter
|
|
Summer
|
Autumn
|
Winter
|
Spring
|
|
2009
|
2.4
|
3.8
|
4.0
|
3.1
|
|
2010
|
2.6
|
4.1
|
4.1
|
3.2
|
|
2011
|
2.6
|
4.5
|
4.3
|
3.3
|
(a) Plot the pattern of energy costs graphically.
(b) Calculate seasonal indexes for the complex's energy costs by the ratio-to- moving-average method.
(c) Find the least squares trendline for energy usage in this office complex.
(d) How much should the financial manager of this office complex budget for energy costs for each quarter of 2012, based on seasonally adjusted trend estimates?
(e) Plot the pattern of energy costs graphically using Excel's Insert > Chart > Line.
(f) Re-compute the least squares trendline for energy usage in (b) using the Line graph and Add Trendline option in Excel.