The dummy variables for the factors in balanced designs are orthogonal. The treatment dummy variables are not orthogonal to the block dummy variables for unbalanced designs. That is essentially what the term "balanced" means.
______________________________________________ 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.