[R-sig-ME] FW: linear mixed model for non-normal negative and continous data
s.blomberg1 at uq.edu.au
Tue Apr 29 03:56:37 CEST 2014
You could try using the Yeo-Johnson transformation in the car package.
On 28/04/14 21:31, Caroline Lustenberger wrote:
> Dear all
> I try to fit a linear mixed model to my data. In short, my dependent variable reflects changes of the bone level (Knmn, in mm), thus this variable is continous and provides negative values. I have two different groups (factor Group) that were measured 3 times each (thus repeated measures, factor Timepoint). I used the following model:
> When performing a qq-plot my residuals are clearly deviant from the norm (long-tailed). Due to negative values I cannot perform classical transformation methods (e.g. log transformation). How could I proccede with this data. Is there a possibility to use a generalized linear model?
> Thanks and all the best
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Simon Blomberg, BSc (Hons), PhD, MAppStat, AStat.
Senior Lecturer and Consultant Statistician
School of Biological Sciences
The University of Queensland
St. Lucia Queensland 4072
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