[R] reading the results of a within subject test

[Ann]

Hi, I ran the following in R (on item means):

aov(VAR ~(a*b)+Error(item/(a*b)), data = item)

I got this result:

Error: item
          Df     Sum Sq    Mean Sq F value   Pr(>F)   
a       1 7.7249e+13 7.7249e+13  11.329 0.003934 **
Residuals 16 1.0910e+14 6.8187e+12                    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Error: item:a
          Df     Sum Sq    Mean Sq F value   Pr(>F)   
a       1 1.1218e+14 1.1218e+14  8.6909 0.009449 **
b     1 2.7264e+10 2.7264e+10  0.0021 0.963912   
Residuals 16 2.0653e+14 1.2908e+13                    
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Error: item:b
            Df     Sum Sq    Mean Sq F value  Pr(>F)  
b       1 6.0538e+13 6.0538e+13  2.7157 0.11886  
a:b  1 1.7894e+14 1.7894e+14  8.0272 0.01199 *
Residuals   16 3.5666e+14 2.2292e+13                  
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Error: item:a:b
            Df     Sum Sq    Mean Sq F value Pr(>F)
a:b  1 4.9726e+12 4.9726e+12   0.629 0.4461
Residuals   10 7.9061e+13 7.9061e+12             

and I'm not sure what is what in there. Is it reporting a between analysis
as well?Why does the interaction between a and b appear several times?

 When I ran the anova I did get a warning message (In aov(VAR ~ (a * b) +
Error(item/(a * b)),  :
  Error() model is singular) 

I'm confused...

Thanks!

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