Mean Squared Error (MSE)
Square each error and average. Smooth to optimize and hard on big misses, but in squared units, so it is often reported as RMSE and minimized as MSE.
-
-
Mean Absolute Error (MAE)
The average absolute gap between forecast and actual, in the target’s own units. Easy to read, linear in the error, and a forecast of the median when minimized.
-
Root Mean Squared Error (RMSE)
Square the errors, average, take the root: same units as the target, but large misses count more. Minimizing it forecasts the mean; it is never below MAE.
-
Regression and Ranking Metrics
A metric is a choice about which errors you will tolerate.