# Y = a + bx for calculating seasonally adjusted sales

Posts: 10Registered
edited November 2017
Hi All,

I came across a calculation which I could not resolve. Perhaps I was not looking from a correct angle. Can someone help me with it? I have attached a picture of the question.

• Posts: 10Registered
edited November 2017
I will start and perhaps someone will add their thoughts on this.

1. I have converted formula to Y = 10,500 + 500x since seasonal variances are in thousands.
2. I have worked out x=9 for 20X3 Q1 (based on 20X1 Q1 = 1)
3. Trend volume for 20X3: Q1 = 15,000, Q2 = 15,500, Q3 = 16,000, Q4 = 16,500
4. No clue afterwards.. What should go to "Time period(x) in Q1 to Q4? I can work out actual data based on trend + variance. But what on earth is this Time period(x)?
• Posts: 10Registered
Maybe Time period(x) is 9 for Q1, 10 for Q2, 11 for Q3 and 12 for Q4.
Then Trend (units) Q1=15,000, Q2=15,500, Q3=16,000, Q4=16,500
Then Seasonally adjusted sales Q1=14,000, Q2=17,750, Q3=17,800, Q4=13,400
Perhaps I've just answered my own question...
• Posts: 10Registered
Do you know what the answer should be?
• Posts: 10Registered
andrew96 said:

Do you know what the answer should be?

Not 100% sure if my assumptions on the latest reply were correct. I do not see any other logical possibility to resolve this.
• Well-Known FarehamPosts: 247Registered
JJ1 said:

Maybe Time period(x) is 9 for Q1, 10 for Q2, 11 for Q3 and 12 for Q4.
Then Trend (units) Q1=15,000, Q2=15,500, Q3=16,000, Q4=16,500
Then Seasonally adjusted sales Q1=14,000, Q2=17,750, Q3=17,800, Q4=13,400
Perhaps I've just answered my own question...

This looks correct to me.
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