The average squared difference between Y ̂_0and Y_0,ε(〖Y ̂_0-Y_0)〗^2, is called the mean squared error of prediction, If the model is correct and prediction is for an individual in the same population from which the data were obtained, so that ε(Y ̂_0-Y_0 )=0, the mean squared error is also the variance of prediction.