The mathematical symbol ! ! is used

The mathematical symbol ! ! is used to indicate the absolute value—that is, it tells you to disregardpositive or negative signs. If MSE, s, or MAD is small, the forecast is typically close to actual demand; bycontrast, a large value indicates the possibility of large forecast errors. The measures do differ in the waythey emphasize errors. Large errors get far more weight in MSE and s because the errors are squared.MAD is a widely used measure of forecast error and is easily understood; it is merely the mean of theabsolute forecast errors over a series of time periods, without regard to whether the error was an overestimate or an underestimate.