<Help Me out!> Maths?
Question: I need to know how to add the 'average seasonal "variation"' of some data, do you know how?
If it help you answer it's on a three point moving average and is to do with sale by a shop.
Answers:
Suppose the data is:
10 15 23 12 17 25 14 19 27
(each facts value will hold an associated time - since you are taking 3-point averages they could well be 4 months apart - ie 3 per year)
To find 3-point moving averages, be in motion along taking three numbers at a time and finding the average:
(10+15+23)/3 = 16
(15+23+12)/3 = 16.67
(23+12+17)/3 = 17.33
and so on.
You will be able to find 7 of these. Each is associated next to the time of the middle number. ie the first average (16) is associated with the time for the number 15 (ie the middle number out of 10, 15 and 23).
You can next plot the original notes and the moving averages on a graph showing the data on the y-axis and time on the x-axis. The unproved data will show seasonal fluctuation - the moving averages will be smoother and show the underlying trend.
You can draw the best fit straight procession through the moving average data and later subtract values from the original background. This will leave the seasonal fluctuation.
It's easier than it sounds!
Hope this help
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