[R] different results aov vs. lm
Prof Brian Ripley
ripley at stats.ox.ac.uk
Fri Sep 30 12:33:29 CEST 2011
On Fri, 30 Sep 2011, Martin Batholdy wrote:
> I currently running regression models on an experimental dataset.
> The model contains one independent continuous variable and two
> independent experimental conditions (one with two factors, the other
> with three factors) and several covariates.
> Now I get different results for a covariate in this model when I run
> aov(modell) vs. lm(modell).
> In the ancova model, one of the covariates seems to explain a
> significant amount of variance. But in the lm-statistics this
> variable doesn't exceed the p-threshold of p = 0.05.
> How can that be?
Apples and oranges? You haven't given us any reproducible code, but I
believe the what you looked at for lm (which does not of itself give
p-values) was equivalent to using drop1, whereas aov gives a
sequential ANOVA table.
I suspect the problem is a lack of statistical understanding, so this
question might better be asked (with an example) of your local
> thanks for any advice on this!
> R-help at r-project.org mailing list
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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