Re: [R] Doubt about nested aov output

From: John Wilkinson (pipex) <wilks_at_dial.pipex.com>
Date: Wed 07 Sep 2005 - 21:03:44 EST


Ronaldo ,

It looks as though you have specified you model incorrectly.

In the Rats example ,the Treatment is the only fixed effect,Rat and Liver are random effects

In aov testing for sig of 'Means' of Random Effects is pointless and that is why 'p' values are not given.Further more the interaction between a Random Effect and a Fixed Effect is also a Random Effect. The 'aov' with error structure terms output reflects this by only giving 'p' values to Fixed Effects and their interactions.

Note That the Fixed Effects of Block, Variety and their interaction Block:Variety are given "p" values while the Field'Random Effects have not.

> model <- aov(Glycogen~Treatment+Error(Rat/Liver))
> summary(model)

Error: Rat

          Df Sum Sq Mean Sq F value Pr(>F) #Rat is random effect Residuals 1 413.44 413.44

Error: Rat:Liver				      #Rat:Liver is Random effect
          Df  Sum Sq Mean Sq F value Pr(>F)
Residuals 4 164.444 41.111

Error: Within

          Df Sum Sq Mean Sq F value Pr(>F) Treatment 2 1557.56 778.78 18.251 8.437e-06 *** #Fixed effect Residuals 28 1194.78 42.67

---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1



I hope that this is of help.

John

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Received on Wed Sep 07 21:00:44 2005

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