Adam,
Take a look at this page for types of sums-of-squares: http://afni.nimh.nih.gov/sscc/gangc/SS.html Not all of them have the property you expect. Bruno > Dear Adam, > > >> I'm just surprised >> that commutativity doesn't hold. >> > > A*B is is not the equivalent notation of any combination of A, B and > A:B. It is only the equivalent of A+B+A:B. When your design is > completely balanced, the output should be the same regardless of the > order. However, with unbalanced/incomplete designs you will get > different outputs. This is because of the famous Type I / Type III > sums of squares issue. To be honest I don't think this is the answer > to your problem, since repeated-measures designs require only 1 data > point per cell. Is any data point missing? > > Francisco > > On 5/14/07, Adam Baker <[EMAIL PROTECTED]> wrote: > >> I wonder if somebody could comment on why I get different summaries >> with these two commands, which differ only in the order of the >> variables. >> >> summary(aov(MidAvg ~ Ccon*Rpres + Error(Subject/Ccon*Rpres),data=nr)) >> summary(aov(MidAvg ~ Rpres*Ccon + Error(Subject/Ccon*Rpres),data=nr)) >> >> With the first command, R doesn't report the main effect of Rpres. >> With the second command, it does (code & output below). It's not very >> important since the interaction is significant; I'm just surprised >> that commutativity doesn't hold. >> >> Thanks, >> Adam >> >> >> >>> summary(aov(MidAvg ~ Ccon*Rpres + Error(Subject/Ccon*Rpres),data=nr)) >>> >> Error: Subject >> Df Sum Sq Mean Sq F value Pr(>F) >> Ccon 1 13245765 13245765 17.767 0.002256 ** >> Residuals 9 6709794 745533 >> --- >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 >> >> Error: Rpres >> Df Sum Sq Mean Sq >> Ccon 1 38923433 38923433 >> >> Error: Subject:Ccon >> Df Sum Sq Mean Sq F value Pr(>F) >> Ccon 2 16646448 8323224 239.589 3.334e-14 *** >> Ccon:Rpres 1 906946 906946 26.107 6.229e-05 *** >> Residuals 19 660053 34740 >> --- >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 >> >> Error: Subject:Rpres >> Df Sum Sq Mean Sq F value Pr(>F) >> Ccon:Rpres 1 645835 645835 9.5416 0.01295 * >> Residuals 9 609176 67686 >> --- >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 >> >> Error: Subject:Ccon:Rpres >> Df Sum Sq Mean Sq F value Pr(>F) >> Ccon:Rpres 2 7636019 3818009 676.48 < 2.2e-16 *** >> Residuals 20 112879 5644 >> --- >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 >> >> Error: Within >> Df Sum Sq Mean Sq F value Pr(>F) >> Residuals 499 9862093 19764 >> >> >> >> >> >> >> >>> summary(aov(MidAvg ~ Rpres*Ccon + Error(Subject/Ccon*Rpres),data=nr)) >>> >> Error: Subject >> Df Sum Sq Mean Sq F value Pr(>F) >> Rpres 1 13245765 13245765 17.767 0.002256 ** >> Residuals 9 6709794 745533 >> --- >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 >> >> Error: Rpres >> Df Sum Sq Mean Sq >> Rpres 1 38923433 38923433 >> >> Error: Subject:Ccon >> Df Sum Sq Mean Sq F value Pr(>F) >> Ccon 2 16646448 8323224 239.589 3.334e-14 *** >> Rpres:Ccon 1 906946 906946 26.107 6.229e-05 *** >> Residuals 19 660053 34740 >> --- >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 >> >> Error: Subject:Rpres >> Df Sum Sq Mean Sq F value Pr(>F) >> Rpres:Ccon 1 645835 645835 9.5416 0.01295 * >> Residuals 9 609176 67686 >> --- >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 >> >> Error: Subject:Ccon:Rpres >> Df Sum Sq Mean Sq F value Pr(>F) >> Rpres:Ccon 2 7636019 3818009 676.48 < 2.2e-16 *** >> Residuals 20 112879 5644 >> --- >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 >> >> Error: Within >> Df Sum Sq Mean Sq F value Pr(>F) >> Residuals 499 9862093 19764 >> _______________________________________________ >> R-lang mailing list >> [email protected] >> https://ling.ucsd.edu/mailman/listinfo.cgi/r-lang >> >> > > > _______________________________________________ R-lang mailing list [email protected] https://ling.ucsd.edu/mailman/listinfo.cgi/r-lang
