Dear useRs, I am using mgcv version 1.7-16. When I create a model with a few non-linear terms and a random intercept for (in my case) country using s(Country,bs="re"), the representative line in my model (i.e. approximate significance of smooth terms) for the random intercept reads: edf Ref.df F p-value s(Country) 36.127 58.551 0.644 0.982
Can I interpret this as there being no support for a random intercept for country? However, when I compare the simpler model to the model including the random intercept, the latter appears to be a significant improvement. > anova(gam1,gam2,test="F") Model 1: .... Model 2: .... + s(BirthNation, bs="re") Resid. Df Resid. Dev Df Deviance F Pr(>F) 1 789.44 416.54 2 753.15 373.54 36.292 43.003 2.3891 1.225e-05 *** I hope somebody could help me in how I should proceed in these situations. Do I include the random intercept or not? I also have a related question. When I used to create a mixed-effects regression model using lmer and included e.g., an interaction in the fixed-effects structure, I would test if the inclusion of this interaction was warranted using anova(lmer1,lmer2). It then would show me that I invested 1 additional df and the resulting (possibly significant) improvement in fit of my model. This approach does not seem to work when using gam. In this case an apparent investment of 1 degree of freedom for the interaction, might result in an actual decrease of the degrees of freedom invested by the total model (caused by a decrease of the edf's of splines in the model with the interaction). In this case, how would I proceed in determining if the model including the interaction term is better? With kind regards, Martijn Wieling -- ******************************************* Martijn Wieling http://www.martijnwieling.nl wiel...@gmail.com +31(0)614108622 ******************************************* University of Groningen http://www.rug.nl/staff/m.b.wieling ______________________________________________ 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.