Question:

A firm that supplies lubricant oils to auto repair garages across Canada has kept record of their last $10$ periods' sales and forecasts in gallons of lubricants. The sales and forecasts are provided in the following Table. Analyze the forecast accuracy of their forecasting system by finding MAD, MSE, MAPE, forecasting bias and tracking signal. Based on the tracking signal, do you suggest that the firm should adjust their forecasting method?

$1.$ Analyze the forecast accuracy of their forecasting system by finding MAD, MSE, MAPE, forecasting bias and tracking signal.

$2.$ Based on the tracking signal, do you suggest that the firm should adjust their forecasting method?