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 place to hash it out, if anything meaningful can indeed be made of it. Cheers, Bert On Tue, Dec 10, 2013 at 5:33 PM, Rolf Turner <r.tur...@auckland.ac.nz> wrote: > > 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 questions >> elicit vague answers). > > > No! Nay! Never! Well, hardly ever. The ***y*** values will rarely be > Gaussian. > (Think about a simple one-way anova, with 3 levels, and N(0,sigma^2) errors. > The y values will have a distribution which is a mixture of 3 independent > Gaussian > distributions.) > > You *may* wish to worry about whether the ***errors*** have a Gaussian > distribution. Some inferential results depend on this, but in many cases > these results are quite robust to non-Gaussianity. > > There. I have exhausted my knowledge of the subject. > > cheers, > > Rolf >> >> >> Cheers, >> Bert >> >> On Tue, Dec 10, 2013 at 6:55 AM, peyman <zira...@gmail.com> wrote: >>> >>> 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 >>> distribution of the data? -- Bert Gunter Genentech Nonclinical Biostatistics (650) 467-7374 ______________________________________________ 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.
