Re: [R] R2 in multilevel modelling

2012-04-30 Thread Kevin Wright
If you want to know if your model fit will your data, then looking at residual-type plots is useful, as can be plotting the model-predictions and observed data together. You might also find interesting "R2 statistics for mixed models" by Matthew Kramer. Beware--as others have indicated, there is

Re: [R] R2 in multilevel modelling

2012-04-30 Thread Joshua Wiley
Hi Chiara, If you just want to compare model fit, you could use a LRT between models where you do and do not estimate the variance/covariance matrix of random effects. R^2 in mixed models do not have the same nice properties they do in fixed effects models. Cheers, Josh On Mon, Apr 30, 2012 at

Re: [R] R2 in multilevel modelling

2012-04-30 Thread Bert Gunter
As you have not provided a clue of what your models are, one can only guess. But if you mean using lots of fixed effects vs a random effect, the answer is that there is no such animal. They are two different non-nested models, and should be chosen based on subject matter considerations. Standar

[R] R2 in multilevel modelling

2012-04-30 Thread klai...@libero.it
Goodmorning everybody, i'm an italian statistician and i'm using R for research. Could someone tell me some indices to see the goodness of fit in multilevel modelling? I'm using the lmer function, and I want to know if my model fit well my data. I actually want to justify the use of multilevel