Or, perhaps I can use Error(subject/(method * problem)) where subject = paste(method, problem)
Because I repeated each simulation several times for different problems of the same problem. This gives me the following output: > summary(aov(performance ~ method * problem + Error(subj/(method * > problem)), data=data)) Error: subj Df Sum Sq Mean Sq F value Pr(>F) method 6 3.3185e+11 5.5308e+10 46.179 3.020e-13 *** problem 1 5.7141e+11 5.7141e+11 477.094 < 2.2e-16 *** method:problem 6 9.8891e+10 1.6482e+10 13.761 3.123e-07 *** Residuals 28 3.3535e+10 1.1977e+09 --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 Error: Within Df Sum Sq Mean Sq F value Pr(>F) Residuals 377 2.0193e+10 5.3562e+07 Warning message: Error() model is singular in: aov(performance ~ method * problem + Error(subj/(method * problem)), data = data) ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.