Mean Squared Error

Synonyms

Quadratic loss; Squared error loss

Definition

Mean Squared Error is a model evaluation metric often used with regression models. The mean squared error of a model with respect to a test set is the mean of the squared prediction errors over all instances in the test set. The prediction error is the difference between the true value and the predicted value for an instance.

$$\displaystyle{mse = \frac{\sum _{i=1}^{n}(y_{i} -\lambda (x_{i}))^{2}} {n} }$$

where y _i is the true target value for test instance x _i , λ(x _i ) is the predicted target value for test instance x _i , and n is the number of test instances.

Cross-References

• Mean Absolute Error