Dear R-community, I am just conducting various mediation analyses with data from individual participants who are nested in teams. I found the “sobel.lme” function to be pretty helpful when doing so. (A big thank you to Paul Bliese for his multilevel-package and the awesome manual!) Here’s the example from the Help-file: data(bh1996) library(nlme) #A small but significant indirect effect indicates leadership mediates #the relationship between work hours and well-being. with(bh1996, sobel.lme(pred=HRS,med=LEAD,out=WBEING,grpid=GRP))
The package estimates three regression models according to standard-mediation-analysis-operating-procedure. Each model has one intercept and one/two slopes. Question 1) Does “sobel.lme” estimate: a) random intercept, fixed slope(s) → as in for example Krull & MacKinnon (2001) Multilevel Modeling of Individual and Group Level Mediated Effects b) random intercept, random slope(s) → Does not necessarily involve a predictor for the slope on level 2 – as this would be phrased moderation rather then mediation (potential matter of dispute, though…). c) fixed intercept, fixed slope(s) → wouldn’t make much sense given the purpose of the function… d) fixed intercept, random slope(s) → wouldn’t make much sense either… Question 2) I know R is sometimes smarter than one would expect after having used other statistical software for years, but… Multilevel Mediations can take in principle three forms (Krull & KacKinnon, 2001; numbers indicate levels): 1->1->1 2->1->1 2->2->1 Is “sobel.lme” really smart enough to “notice” that a variable is constant within groups and therefore assigns it to the group level accordingly? If not, it would probably help to know which of the above three mediation-forms is implemented in the function. Thanks for reading this lengthy mail. It would be really nice if anyone could tell me (and the help-archive) anything regarding these two questions. Cheers Sebastian -- Dipl.-Psych. Sebastian Stegmann Goethe University, Frankfurt, Germany ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
