Graphing Confidence Ellipses: An Update of Ellip for Stata 8

Abstract

This paper describes an update of the ellip command for graphing confidence ellipses in Stata 8. Two of the most notable new features are the option to graph confidence ellipses around variable means and the ability to add inscribed lines. These features allow a geometric characterization of linear regression with unequal error variances, as in McCartin (2003).