Hi there,I need advice in longitudinal data/repeated measure analysis. In particular, I have some difficults about the fixed effect of time in these type of studies. With only two repeated measures, taken on the same subject two times (2001 and 2012) and if I want to detect if the response variable is different between the two measures  (2001 and 2012), how should I treat the time effect? As a continuos variable or a grouping factor?The measure were taken in 2001 and in 2012. If I explicit time as a continuous variable the model (linear mixed model) doesn't reach the convergence, because in this case, the intercept represent the measurement at time 0. Perhaps I should assign the value of 0 and 11 respectively to 2001 and 2012, or treat time as a grouping factor (time a and time b)?Thanks in advanceLudovico
                                                                                                                                
Ludovico
Frate

PhD student (University of Molise - Italy)
Environmetrics Lab
http://www.distat.unimol.it/STAT/environmetrica/organico/collaboratori/ludovico-frate-1
Department of Biosciences and Territory - DiBT
Università del Molise.
Contrada Fonte
Lappone, 
86090 -  Pesche (IS)
ITALIA.
Cel: ++39
3333767557
Fax: ++39 (0874) 404123
E-mail ludovico.frate@unimol.it
ludovicofrate@hotmail.it
 		 	   		  
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