Mean absolute percentage error

Mean absolute percentage error (MAPE) is a way of measuring how close a set of numbers (like predictions) are to a "real" set of numbers (like actual results). The way it works is to take the average of the absolute values of the differences between the "real" numbers and the "predicted" numbers, expressed as a percentage of the "real" numbers. That way, MAPE can show us how much error there is, on average, between the numbers we predicted and the numbers that actually happened.