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12.2: Chapter 5

Principles of Data Science · LibreTexts

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    Quantitative Problems

    1.
    Most likely, the period would be 52, as sales probably go through a cycle each year, and there are 52 weeks in the year.
    2.
    a.
    There are peaks in the data at times 1, 5, and 9 as well as minimum points at times 4, 8, and 12, suggesting a period of 4 months.
    b.
    (728.6, 729.4, 728.6, 727.3, 727.1, 727.0, 726.0, 725.8)
    There will be 8 terms in the centered SMA, as shown. These values form the trend-cycle component.
    c.
    (69.9, −225.3, 159.8, −1.5, 66.3, −228.0, 165.7, −3.8)
    d.
    (68.1, −226.65, 162.75, −2.65), repeating in blocks of 4
    e.
    (812.6, 953.85, 635.75, 506.75, 820.3, 952.45, 630.65, 501.65, 823.6, 948.65, 626.35, 504.25)
    3.
    a.
    Since the missing data is due to different reporting policies on different days of the week, an SMA window of 7 days is most appropriate.
    b.
    See Solution Manual
    4.
    a.
    from the ACF plot.
    b.
    See Solution Manual
    5.
    Forecasted value for 2024: 1.2124
    6.
    a.
    . . , or 12.3%. , or 13.3%.
    b.
    See Solution Manual

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