13. Using standard deviations for the values obtained in parts

a, b, and c of problem 12, compare your results to the results of a Cumberland Company survey of its managers concerning the accuracy of the company’s forecasts (shown below).

Expected Forecast Error for a Period of:

Level of Detail 1 Month 1 Quarter 1 Year Total Volume Family 12* 8 8 Type in Family 15 10 8 Grade in Type 15 NF† 12 SKU‡ 30 NF NF

*±12%.

†NF = no forecast.

‡Stockkeeping unit.