# Robust ANCOVA literature

I am looking for some source of information, some articles about Robust ANCOVA. Can you suggest me something? And do you know any source that directly gives information about how to perform various robust ANCOVA with R?

I have seen a citation about Maxwell et al. 1993, an article called Analysis of Covariance but I do not find it!

I know Quinn and Keough, Experimental Design and Data Analysis for Biologists but they do not give much information about Robust ANCOVA.

• In English, unlike French, question marks are not preceded by a space (I am commenting on this issue because I noticed you did it in your previous questions as well). – Gala Jul 25 '13 at 20:55
• @GaëlLaurans Thanks for that comment; it's helpful to this non-Francophone - now that I know why that happens so often, I will be more understanding of it. – Glen_b -Reinstate Monica Jul 25 '13 at 22:48

Look for material on robust regression. There is lots of it.

ANCOVA, ANOVA and regression are all the same model, really. In matrix algebra terms they are all

$Y = X\beta + \epsilon$

A general approach is to use cumulative probability ordinal models, the most popular being the proportional odds ordinal logistic model. See a case study in R in Chapter 15 of my Handouts.