On Mon, Jun 1, 2009 at 7:50 PM, tsunhin wong <thjw...@gmail.com> wrote: > But I have some follow-up questions: > 1. In aov, why IVs (subject & condition) cannot be in number format?
Put simply, because that's the only way to obtain the values you observe in the paper you're reading. :Op Factorizing tells the ANOVA that the labels associated with each level of the factor aren't really meaningful. This is particularly evident in the case of Subject numbers, which (typically) have no numeric interpretation (Ss #6 is not 2 times Ss #3). The original authors' choice to treat condition as a factor was a less clear choice given that it clearly refers to a measurable ratio quantity (seconds). I presume the paper to which you're referring is the Masson & Loftus 1994 paper (be sure to read their 2003 follow-up and 2004 correction). In that case the authors come from a field where it's commonplace to treat even ratio independent variables as factored. > 2. Why I need to use factor() on IVs (subject & condition) but I > cannot use factor() on DV (recall)? As noted above, factoring prohibits R from interpreting the labels of a value as numerically meaningful, something you surely do not want to do with your DV in this example. -- Mike Lawrence Graduate Student Department of Psychology Dalhousie University Looking to arrange a meeting? Check my public calendar: http://tr.im/mikes_public_calendar ~ Certainty is folly... I think. ~ ______________________________________________ R-help@r-project.org 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.
