[R] replicates in repeated ANOVA

[John Vokey]

Michael,
   You have mis-specified the aov() call.  It should be:

rt.aov=aov(rt~Group*rep*prepost+Error(subj/(prepost*rep)),data=rt)

  yielding:

summary(rt.aov)

Error: subj
           Df Sum Sq Mean Sq F value Pr(>F)
Group      1 3864.7  3864.7  2.2941 0.2044
Residuals  4 6738.6  1684.6

Error: subj:prepost
               Df  Sum Sq Mean Sq F value Pr(>F)
prepost        1  250.69  250.69  0.9934 0.3753
Group:prepost  1  568.03  568.03  2.2509 0.2079
Residuals      4 1009.44  252.36

Error: subj:rep
           Df  Sum Sq Mean Sq F value Pr(>F)
rep        2  325.50  162.75  0.4882 0.6309
Group:rep  2   74.39   37.19  0.1116 0.8958
Residuals  8 2667.11  333.39

Error: subj:prepost:rep
                   Df  Sum Sq Mean Sq F value Pr(>F)
rep:prepost        2  463.39  231.69  0.9295 0.4336
Group:rep:prepost  2  338.72  169.36  0.6794 0.5339
Residuals          8 1994.22  249.28


On 14-Apr-07, at 4:00 AM, r-help-request at stat.math.ethz.ch wrote:

> Unfortunately, whenever, I put the Group factor in the Error term  
> (to take into account subj:Group as a random effect), I get a  
> singular result: (see the data entry section below)
>
>> rt.aov <- aov(rt ~ Group*prepost + Error(subj/(prepost*Group)),  
>> data=rt.df)
>         Warning message:
>         Error() model is singular in: aov(rt ~ Group * prepost +  
> Error(subj/(prepost * Group)), data = rt.df)