Standardized regression residual ($e_i/[s\sqrt{1-h_{ii}}]$)

In a normal linear model, the $i$th regression residual has variance ${\sigma }^2(1-h_{ii})$, where $h_{ii}$ is a diagonal entry of the hat matrix. Replacing $\sigma$ by the residual standard deviation $s$ gives the standardized residual used in the normal Q-Q plot of R's linear-model diagnostic plots.