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Hello Gromit
my question is in relation to question Q2a – December 2013.
i do not understand how the model answer came up with the predicted value for quarter 3 of 2013 for 173•55.
however i applied the method in your lecture and i am coming up with something close to 171 which is different from the model answer of 173•55 but still close.
will i get marks if i apply your method?
please advise.
the numbers are slightly out but interpretation would be the same
thanks
I would do it as followsThe trend figure goes from 131 to 146.25 in 9 increments, so 15.25/9 = 1.69 per season.
To go from the last trend figure at 2012 Q4 to Q3 2013 would raise the trend figure by 3 x 1.69 from 146.25 to 151.32
The seasonal variation for Q3 is +22.25, so the predicted figure for 2013 Q1 is 151.32 + 22.25 = 173.57.
You must understand that we are scrabbling to predict the future using statistical analysis. Different analyses will produce slightly different answers. As long as the method is sensible you will be fine.
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