Littlefield Laboratories is a state-of-the-art highly automated blood samples testing lab. The demand of blood sample testing for the previous 20 days (day 1 to day 20) are given in the EXCEL file "LF demand.xls" on Blackboard. You are asked to perform demand forecast for day 22. There are two steps to that end. First you need to choose a "best" forecasting model and, second, use that model to forecast demand on day 22. The manager does not specify which forecasting model you should use, so you need to compare different forecasting models to determine the appropriate one to use. You consider the following four models.

To see which model works the best, you need to compare their forecast accuracy for demand in the past. In other words, you compare their forecast accuracy for days 5 to 20 (comparing days 5 to 20 because you can derive forecasts for every model starting on day 5).

a. Please calculate forecasts and MAPE of each of the four forecasting models for days 5 to 20.

b. Please plot actual demand for days 1 to 20, forecasts of moving average for days 5 to 20 on the same chart in EXCEL. You should see that forecasts of moving average lag behind the trend.

c. Which forecasting model generates the smallest MAPE? You will pick that model to forecast demand for day 22 because historically it produces the smallest forecast error. Please forecast demand for day 22 using the model with the smallest MAPE.