[R-sig-ME] Mean Centering Data in Linear Mixed Models

[Hufthammer, Karl Ove]

You might want to take a look at the paper 'Centering Predictor Variables in Cross-Sectional Multilevel Models: A New Look at an Old Issue', available at:
http://www-bcf.usc.edu/~sping/PM-515/references/Enders%202007%20centering%20in%20multilevel%20analysis.pdf

There are some subtle conceptual issues with regards to centering of predictor variables, carefully explained in this (18 pages long!) paper.
 

Karl Ove Hufthammer



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Sendt: 24. august 2013 02:43
Til: r-sig-mixed-models at r-project.org
Emne: [R-sig-ME] Mean Centering Data in Linear Mixed Models

Hi all,

I have a data set that includes 1 predictor variable (ambient noise) that is continuous and 2 predictor variables that are factors.  One of the predictor variables has 12 levels, that has 59 individuals (random effect) grouped within (unevenly).  The question is, should I consider mean centering my continuous predictor variable?  I know that interpretation of the model results means that the intercept and slope are based on ambient noise of 0 dB.  If I do want to mean center my data, is there a specific way I should do this because of the predictor variable that has individuals grouped within?  Thank you for your help.

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