leverage analysis vs. case deletion

From: "Bonate, Peter" Peter.Bonate@genzyme.com Subject: [NMusers] leverage analysis vs. case deletion Date: Tue, 2 May 2006 12:26:41 -0400 They are not synonyms. You can do a leverage analysis using case deletion but with linear models you do not need to do so. You can use the HAT matrix in a linear model to get the leverage a subject exerts in a dataset. With a nonlinear model with individual level data (no repeated data), you can get the same measure of influence using the Jacobian matrix. With a linear mixed effects model there are ways to do this but they are not easy and require access to software that allows matrix calculations, like MATLAB or SAS IML. But with a nonlinear mixed effects model, I am not aware of how you could get this data without doing case deletion. Whenever I can, I do a case deletion analysis on my data (time permitting) since you can also get the jackknife estimate of the standard errors. Hope this helps, pete Peter L. Bonate, PhD Genzyme Corporation Director, Pharmacokinetics 4545 Horizon Hill Blvd San Antonio, TX 78229 USA peter.bonate@genzyme.com phone: 210-949-8662 fax: 210-949-8219