Outliers and Leverage in Regression

The applet below is designed to show the effect of outlienrs and leverage points on a regression line. You can place an additional point on the plot by clicking the mouse button; click again to move the point to a new location. Adding the point close to the existing line barely changes the line. Adding the point far from the existing line changes the line considerably. This is particularly true if the new point is placed outside the range of the original data.

This example was created by R. Webster West, Dept. of Statistics, Univ. of South Carolina.