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 > -- Francisco Torreira PhD Candidate in Romance Linguistics University of Illinois at Urbana-Champaign https://netfiles.uiuc.edu/ftorrei2/www/index.html tel: (+1) 217 - 778 8510 _______________________________________________ R-lang mailing list [email protected] https://ling.ucsd.edu/mailman/listinfo.cgi/r-lang
