 This is expected intuitively – the variance of the population of formula_19 values does not shrink when one samples from it, because the random variable "εi" does not decrease, but the variance of the mean of the formula_19 does shrink with increased sampling, because the variance in formula_21 and formula_22 decrease, so the mean response (predicted response value) becomes closer to formula_23.This is analogous to the difference between the variance of a population and the variance of the sample mean of a population