2. Given below are 36 months of sales data from Redwood Rummage Company. Construct a spreadsheet to calculate an exponential smoothing forecast for each month, using a forecast of 450 for the first month. Use a column for each of the following: month number, demand, forecast, error, a X error, absolute error, error squared, percentage error, and absolute percentage error. Sum the appropriate columns from month 13 through month 36 to compute the mean absolute deviation, mean square error, and mean absolute percentage error. Perform the first computations with a = 0.1, and record the measures of error for this

a. Change « to 0.2 and repeat; then use a of 0.3. When the MAD starts to increase, you have passed the best « (as measured by the MAD). By changing a in steps of 0.02 (use a two-decimal-place value of «), search near the best value of a found so far. Which of these values of a makes the MAD the smallest?

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MONTH DEMAND MONTH DEMAND 1 447 19 411 23 652 501 4 627 2222 20 351 21 477 553 5 549 23 522 6 407 24 610 7 309 25 567 8 436 26 555 9 450 27 669 10 557 28 552 11 466 29 505 12 613 30 436 13 478 31 471 14 662 32 376 15 558 33 394 16 552 34 452 17 586 35 538 18 544 36 575