When there are no outliers
Firstly mention that all residuals do not have the same standard deviation — their standard deviation is highest for points whose x-value is near the mean x-value of the data. Standardised residuals divide each residual by an estimate of its standard deviation. Standardised residuals far from zero are often used to indicate outliers.
Click Another Data Set a few times. Then repeat with larger sample sizes.
In large data sets, do not assume that standardised residuals outside ±3 must be outliers — values a little outside can occur by chance.