# Nelson Industries manufactures a part for a type of aircraft engine that is becoming obsolete. The sales

## Question:

Nelson Industries manufactures a part for a type of aircraft engine that is becoming obsolete. The sales history for the last 10 years is as follows:

| Dec-08 | Dec-09 | Dec-10 | Dec-11 | Dec-12 | Dec-13 | Dec-14 | Dec-15 | Dec-16 | Dec-17 |

| 945 | 875 | 760 | 690 | 545 | 420 | 305 | 285 | 250 | 210 |

| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |

a). Plot sales versus time.

b). Estimate the regression model for a linear time trend of sales.

c). What is the mean absolute percent error of the linear regression estimates for these 10 years?

d). Using this model, estimate sales for year 11.

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**Related Book For**

## Forecasting And Predictive Analytics With Forecast X

**ISBN:** 978-1259903915

7th edition

**Authors:** J. Holton Wilson, Barry Keating