Forecast error

In statistics, a forecast error is the difference between the actual/real and the predicted/forecast value of a time series or any other phenomenon of interest.

Forecast Error can be a calendar forecast error or a cross-sectional forecast error, when we want to summarize the forecast error over a group of units. If we observe the average forecast error for a time-series of forecasts for the same product or phenomenon, then we call this a calendar forecast error or time-series forecast error. If we observe this for multiple products for the same period, then this is a cross-sectional performance error.