Re: [R] data distribution for lme

2013-12-11 Thread Kevin Wright
On Tue, Dec 10, 2013 at 7:33 PM, Rolf Turner r.tur...@auckland.ac.nzwrote: See inline below. On 12/11/13 11:28, Bert Gunter wrote: This is not really an R question -- it is statistics. In any case, you should do better posting this on the R-Sig-Mixed-Models list, which concerns itself

[R] data distribution for lme

2013-12-10 Thread peyman
Hi folks, I am using the lme package of R, and am wondering if it is assumed that the dependent factor (what we fit for; y in many relevant texts) has to have a normal Gaussian distribution? Is there any margins where some skewness in the data is accepted and how within R itself one could check

Re: [R] data distribution for lme

2013-12-10 Thread Bert Gunter
This is not really an R question -- it is statistics. In any case, you should do better posting this on the R-Sig-Mixed-Models list, which concerns itself with matters like this. However, I'll hazard a guess at an answer: maybe. (Vague questions elicit vague answers). Cheers, Bert On Tue, Dec

Re: [R] data distribution for lme

2013-12-10 Thread Andrew Robinson
No - it is assumed to be conditionally normal, that is, normal conditional on the model. So you should be looking at the distributions of the residuals rather than of the response variable, as an indicator for whether or not the model assumptions are satisfied. Skewness in the residuals may or

Re: [R] data distribution for lme

2013-12-10 Thread Rolf Turner
See inline below. On 12/11/13 11:28, Bert Gunter wrote: This is not really an R question -- it is statistics. In any case, you should do better posting this on the R-Sig-Mixed-Models list, which concerns itself with matters like this. However, I'll hazard a guess at an answer: maybe. (Vague

Re: [R] data distribution for lme

2013-12-10 Thread Bert Gunter
Thanks Rolf and Andrew. I was entirely too careless and should take a trip to the woodshed (google David Stockman woodshed for the reference). The correct answer therefore is: maybe for the residuals, for the right model, of course. But I still think the crowd on r-sig-mixed-models is the right