[R] how to run ANCOVA?
sasha.wolosin at gmail.com
Wed Aug 23 16:29:34 CEST 2006
Thank you very much for your response!
However, I still do not understand how this works. I would like to
adjust the factors (diagnosis and gender) for the covariate (age), so
you are saying I should use:
aov.out <- aov(response ~ age + diagnosis*gender, data)
aov.out <- aov(response ~ age*diagnosis*gender, data)
But how is that different from just a 3-way ANOVA with age, diagnosis,
and gender as the the three effects? Isn't ANCOVA a fundamentally
On 8/23/06, Richard M. Heiberger <rmh at temple.edu> wrote:
> > aov.out <- aov(response~diagnosis*gender,data)
> Just add it where you think it belongs in the
> sequential sum of squares
> To adjust the factors for the covariate use
> aov.out <- aov(response ~ age + diagnosis*gender, data)
> To adjust the covariate for the factors
> aov.out <- aov(response ~ diagnosis*gender + age, data)
> If you want to check for interaction of the factors with the
> covariate, then use * instead of + in the formula.
> Please note that I added spaces to your statement to improve human legibility.
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