
Chapter 16
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when compared to the linear regression model. This comparison can be easily understood with
the tted line plot (linear) and tted line plot (quadratic) exhibited in Figures 16.65 and 16.66
produced using Minitab.
From Figure 16.64, the quadratic trend forecasting equation can be stated as below:
Pro t after tax = 5543 + 168.6 (Time period) + 182.6 (Time Period)
2
The estimated pro t after tax in 2010–2011 can be obtained by substituting time period = 22 in the
quadratic trend forecasting equation given. So, the estimated pro t after tax for year 2010–2011 is
Pro t after tax = 5543 + 168.6 × (22) + 182.6 × (22)
2
= 97630.6 million ...