A textbook publishing company has compiled data on total annual sales of its bus

Question

A textbook publishing company has compiled data on total annual sales of its business texts for the preceding nine years:

a. Using an appropriate model, forecast textbook sales for each of the next five years. (Round your intermediate calculations to 3 decimal places and final answers to 2 decimal places.)

b. Compute +/- 2s control limits for the control chart for forecast errors using just data from the original nine periods. (Round your intermediate calculations to 4 decimal places and final answer to 2 decimal places.)

Control limits are 0 ±             

c. Suppose actual sales for the next five years turn out as follows:
       

Is the forecast performing adequately?

Yes

No

Year 1 2 3 4 5 6 7 8 9 Sales (000): 37.10 45.00 49.80 51.00 54.60 57.60 63.40 68.80 74.90

Explanation / Answer

A.

so,

using this :

B.

So using 2S:

C.

n= 9 X Y X^2 XY Year Sales (000): 1 37.1 1 37.1 2 45 4 90 3 49.8 9 149.4 4 51 16 204 5 54.6 25 273 6 57.6 36 345.6 7 63.4 49 443.8 8 68.8 64 550.4 9 74.9 81 674.1 45 502 285 2767.4 a = 34.4333 b = 4.2733 Y = a+ bX r= 0.968527

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