 More generally, the FVU will be 1 if the explanatory variables "X" tell us nothing about "Y" in the sense that the predicted values of "Y" do not covary with "Y".But as prediction gets better and the MSE can be reduced, the FVU goes down.In the case of perfect prediction where formula_9 for all "i", the MSE is 0, "SS"err = 0, "SS"reg = "SS"tot, and the FVU is 0.