A textbook publishing company has compiled data on total annual sales of its business textbooks for the preceding eight years:
| Year: | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| Sales(000): | 37.80 | 43.20 | 49.00 | 50.50 | 54.50 | 58.90 | 63.20 | 68.30 |
a-1. Select the correct data chart and fit an appropriate model to it.
| Chart A | Chart B | Chart C |
(Click to select) Chart A Chart B Chart C
a-2. Forecast the preceding eight years, and determine the forecast errors. (Negative answers should be indicated by a minus sign. Do not round intermediate calculations and round your final answer to 2 decimal places.)
| Year | Sales(000) | Forecast | Error | Error?2 |
| 1 | 37.80 | |||
| 2 | 43.20 | |||
| 3 | 49.00 | |||
| 4 | 50.50 | |||
| 5 | 54.50 | |||
| 6 | 58.90 | |||
| 7 | 63.20 | |||
| 8 | 68.30 | |||
a-3. Construct 2s control limits. (Round the final answer to 2 decimal places.)
2s control limits are ±
b. Using the model, forecast textbook sales for each of the next five years. (Round the final answers to 1 decimal place.)
| Year | Sales(000) | Forecast | Error |
| 9 | 74.40 | ||
| 10 | 77.30 | ||
| 11 | 82.90 | ||
| 12 | 88.60 | ||
| 13 | 93.90 | ||
c. Suppose actual sales for the next five years turn out as follows:
| Year: | 9 | 10 | 11 | 12 | 13 |
| Sales(000): | 74.40 | 77.30 | 82.90 | 88.60 | 93.90 |
Calculate the forecast errors for years 9 to 13. Is the forecasting process in control?
(Click to select) Yes No