The stock price on the first day of the month for The Boeing Corporation from January $1970$ to December $2009$ is provided in the spreadsheet: The Boeing Corporation Stock Prices $.$

In column C we have implemented an exponential smoothing model, which is parameterized by the initial estimate of the permanent component given in cell D$1$ and the smoothing parameter $\backslash$alpha given in cell F$1.$

In column D we give the one$-$month$-$ahead forecast for the stock price, and then in columns E$,$ F$,$ G$,$ H we calculate the monthly error terms needed to compute MAD, RSME, and MAPE $($cells K$2,$ L$2,$ M$2)$