Forecasting Answer Manual

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CHAPTER 3

Forecasting

1. a. Plotting each data set reveals that blueberry muffin orders are stable, varying around an average. Therefore, the naïve forecast is the last value, 33. The demand for cinnamon buns has a trend. The last change was from 31 to 33 (33 – 31 = 2). Using the last value and adding the last trend change, the forecast is 33 + 2 = 35. Demand for cupcakes has an apparent seasonal variation with peaks every five days. Day 1 = 45, Day 6 = 48 and Day 11 = 47. Since the peaks occur every five days, the next peak would be at Day 16.

b. The use of sales data instead of demand implies that sales adequately reflect demand. We are assuming that no stock-outs occurred because demand equals sales if there are no shortages.

2. a.

b. 1)

| | |t |Y |tY | |

| | | | | |From Table 3–1 with n = 7, (t = 28, (t2 = 140 |

| | | | | |[pic] |

| | | | | |[pic] |

| | |1 | 19 | 19 | |

| | |2 | 18 | 36 | |

| | |3 | 15 | 45 | |

| | |4 | 20 | 80 | |

| | |5 | 18 | 90 |...