I'm trying also to understand how to get the between-group variance out of a one-way ANOVA, but I'm beginning to think that in a sense, the variance does not exist. Emma said:
*The model is response(i,j)= group(i)+ error(i,j)* Yes, if by group(i) you mean intercept + coefficient[i]. *we assume that group~N(0,P^2) and error~N(0,sigma^2) * Only the error is assumed to be a random variable. Group is a fixed effect, not a random variable, and therefore it has no variance associated with it. The model does not predict a variance for it. One could compute the variance of the coefficients and call this a group variance, but it seems to me that isn't the right way to think about it. I'm trying to calculate a heritability value for a trait in an organism, defined as Vg/Vp, where Vg = variance due to genotype and Vp = total variance. The model is p~g, or p[i,j] = intercept + g_coefficient[i] + error[i,j]. But to get Vg, I think it is actually necessary to use a different model, where g is modelled as a random variable (a random effect), so the model can estimate a variance associated with it. If anyone can add something to this, please do. ted -- View this message in context: http://r.789695.n4.nabble.com/Between-group-variance-from-ANOVA-tp901535p4637686.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.
