Hmwk Problems: Forecasting

Problem 4:

An electrical contractor’s records during the last five weeks indicate the number of job requests:

Week: 1 2 3 4 5

Requests: 20 22 18 21 22

Predict the number of requests for week 6 using each of these methods:

a. Naïve

b. A four-period moving average

c. Exponential smoothing with a smoothing constant of .30. Use 20 for week 2 forecast.

Problem 7:

Freight car loadings over a 12-year period at a busy port are as follows:

Week Number Week Number Week Number

1 220 7 350 13 460

2 245 8 360 14 475

3 280 9 400 15 500

4 275 10 380 16 510

5 300 11 420 17 525

6 310 12 450 18 541

a. Determine a linear trend line for freight car loadings.

b. Use the trend equation to predict loadings for weeks 20 and 21.

c. The manager intends to install new equipment when the volume exceeds 800 loadings per week. Assuming the current trend continues, the loading volume will reach that level in approximately what week?

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Problem 28:

Two independent methods of forecasting based on judgement and experience have been prepared each month for the past 10 months. The forecasts and actual sales are as follows:

Month Sales Forecast 1 Forecast 2

1 770 771 769

2 789 785 787

3 794 790 792

4 780 784 798

5 768 770 774

6 772 768 770

7 760 761 759

8 775 771 775

9 786 784 788

10 790 788 788

a. Compute the MSE and MAD for each forecast.

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