2.4.Evaluating Forecast The forecast error e,in period t is the difference between the forecast value for that period and the actual demand for that period. e,=F-D The three measures for evaluating forecasting accuracy during n period MD=∑Ie,l MsE=∑e MAPE=[∑1e,/D,IxI00 n i=l n i=1 n i=l MAD:The mean absolute deviation,preferred method; MSE:The mean squared error; MAPE:The mean absolute percentage error(MAPE) The forecast error et in period t is the difference between the forecast value for that period and the actual demand for that period. ttt e FD    The three measures for evaluating forecasting accuracy during n period 2 1 1 n i i MSE e n    • MAD: The mean absolute deviation, preferred method; • MSE: The mean squared error; • MAPE: The mean absolute percentage error (MAPE) 1 1 | | n i i MAD e n    1 1[ | / |] 100 n i i i MAPE e D n     2.4. Evaluating Forecast