Re: [R] marginality principle / selecting the right type of SS for an interaction hypothesis

From: hadley wickham <h.wickham_at_gmail.com>
Date: Mon, 26 May 2008 06:17:19 +1200

> BTW, although I didn't read it carefully, the your web-page description of a
> main effect in the presence of an interaction appears to imply that this
> averages across all individuals, when in fact it averages across the levels
> of the other factor; the result is different when there are unequal numbers
> of observations in the cells. As well, you describe the model in your email
> as an ANCOVA, when in fact it appears to be a two-way ANOVA.

And why not show the raw data on the model summary plots? That way you could spot potential outliers, or skewness etc.

Hadley

-- 
http://had.co.nz/

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