Dear Meike, a variable with negative entry for J in IJ (I cannot become negative) explains more in the joint model than it can explain when alone in the model. You can find discussions of such phenomena e.g. under the key word "suppression" or "suppressor variables".
And by the way, as you are using hier.part, you might also be interested in the package relaimpo (linear model with R-squared only, but more different metrics for partitioning). Regards, Ulrike ****************************** Prof. Dr. Ulrike Grömping Fachbereich II TFH Berlin Luxemburger Str. 10 13353 Berlin www: www.tfh-berlin.de/~groemp/ ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
