[R] two-way anova nested fix effects issues

From: Hufkens Koen <koen.hufkens_at_ua.ac.be>
Date: Tue 03 Apr 2007 - 13:20:32 GMT


Hi list,  

I have some anova issues...
I have a dataset comprised of two factor values and a dependent value. The factors are patchiness and within patchiness I have 4 treatments. So factor treatment is nested within factor patchiness. The dependent variable is a lenght.  

If I'm not mistaken my model would be:  

model <- aov(length ~ patchiness + patchiness/treatments)  

However there are a few issues:  

First, the design is unbalanced because of missing values Second, the variances across the different treatments and patchiness levels is not equal (probably due to the patchiness level changes) Third, the second parameter and the fact that the values are in a way discrete produce a non normal distribution and heteroscedacity in my residuals if is ignore everything and run the above model.  

So is there still a way to tell if there is a difference in length for the different patchiness levels and treatments?  

Kind regards,
Koen

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Received on Tue Apr 03 23:22:50 2007

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