time series

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    fauz
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    The following variations and trend have been calculated for sales over a period of time using additive model:

    seasonal variation
    quarter 1 +25
    quarter 2 -10
    quarter 3 -30
    quarter 4 +15

    trend +50 per quarter
    the last known trend reading was taken in year 3,quarter 3 and was $1750

    Question:what would be the time series value for year 4 quarter 3?

    please help!!!!


    Avatar of John Moffat
    John Moffat
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    The last trend reading was year 3 quarter 4. So, by year 4 quarter 3, three more quarters have passed. So the trend forecast will be 1750 + (3 x 50) = 1900.

    Quarter 3 has a seasonal variation of -30, so the actual forecast for year 4, quarter 3 will be 1900 – 30 = 1870.


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    fauz
    Participant
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    thanks for the reply sir, but the answer on the answer sheet is $1920. I’m confused.


    Avatar of John Moffat
    John Moffat
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    Sorry – my fault.

    There are four more quarters (not three) from year 3 quarter 3 to year 4 quarter 3.

    So the trend forecast will be 1750 + (4 x 50) = 1950.

    Quarter 3 has a seasonal variation of -30, so the actual forecast is 1950 – 30 = 1920.

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