Dear R users, I am looking for an easy (i.e., direct) way of obtaining the F and p values from the intercept in anovas with within-subject designs. My data are from a psychophysics experiment where I am using d' (d-prime) values obtained from 3 modalities of presentation in each subject. I would like to know not only whether there is an effect of modality, but also whether the main effect is significant (meaning that d' > 0). I know that a t.test again the null mean would provide me with similar stats on the main effect, but I would like to get those stats in an F form, for consistency with the stats on the other factors of interest.
As far as I understand how R works, the function "anova" provides you with such information but it is restricted to between-group analyses. For within-subject designs, one has to use "summary(aov)" but stats on the intercept are not included in the result of this function. I have pasted an example below. As one can see, only the Sum of Sq and Mean Sq are given for the main effect. Thank you for any advice you can provide, -Sid summary(aov(x~mod+Error(suj/(mod)), data=dp)) Error: suj Df Sum Sq Mean Sq F value Pr(>F) Residuals 10 19.5977 1.9598 Error: suj:mod Df Sum Sq Mean Sq F value Pr(>F) mod 2 8.2475 4.1237 4.2955 0.02806 * Residuals 20 19.2005 0.9600 ---Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 Error: Within Df Sum Sq Mean Sq F value Pr(>F)Residuals 33 55.812 1.691 ______________________________________________ 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.
