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Forums › Ask ACCA Tutor Forums › Ask the Tutor ACCA MA – FIA FMA › Mock questjon time series
A company uses a multiplicative time series model to forecast sales. The trend in sales is linear and is described by the following equation:
Trend= 400+10T
Where T=1 denotes the first quarter of 20X0
T=2 denotes the second quarter of 20X0 etc
The average seasonal variations are as follows:
Quarter 1 2 3 4
% variation -30 +40 +10 -20
Ans is 517 units but my ans is 480
400+10×70=470
470+10=480
In the ans they have multiplied 470 with 1.1 I unable to figure out the derivation of that 1.1 figure ,if u could help me out it would be great
The variations given in the question are % variations.
So the forecast is 470 + (10% x 470) = 517
But sir here they are using multiplicative model so how is (10/100×470) added shouldn’t it be mulitiplied
Adding 10% is multiplicative. It is the same as taking 110%.
OK sir thank you so much ,sir if this question was based on additive model then the ans would have been 480
Yes, although then the variation would be given as 10 and not as 10%.
Thank you so much sir
You are welcome.
