The table below shows the sales of new cars by quarters during a period of
three years:

Year Quarter 1 Quarter 2 Quarter 3 Quarter 4
Sh. “million” Sh. “million” Sh. “million” Sh. “million”
2001 55.0 76.5 61.2 77.8
2002 54.4 65.9 52.7 81.4
2003 59.3 83.2 78.5 93.0
Required:
(i) Explain the purpose of the seasonal index (5
marks)
(ii) The seasonal index for each quarter assuming an additive model. (15
marks)